Sorry for not responding earlier. I'm preparing a case for the Manitoba Court of Appeal, and it's taking all my time. I'm not a lawyer, and that's presumably what makes it harder.
To answer your questions:
If you only used hydraulic cement in two spots, I wouldn't bother replacing it. It's not like the entire lattice mortar is stronger than the bricks. Maybe next time you're doing any brickwork and you have the tools out anyhow, see if you can pull out the old hydraulic cement and replace it with mortar. You probably won't be able to cuz hydraulic cement expands as it cures, and I expect it's wedged into that brickwork real tight by now. If you can't get it out, forget about it. If you can, replace it.
You could always drill through the hydraulic cement with a masonary bit and hammer drill, and then chip the hydraulic cement to pieces with a small chisel.
But i have a question on the foam. its sounds like it will only fill in between the studs. wont the outside of the studs still be exposed??
Sure, but leaving the wall studs exposed on their outside will only result in a bit of heat loss. Remember that the R value of wood is approximately 1 per inch. So a wall stud offers an R value of about 3.5 compared to a 3.5 inch thick slab of extruded foam insulation that will give you about 17. So, eventually, if you smoke or burn candles in your house, you might expect to see dark lines forming over the wall studs due to something called "Brownian Motion" which is where tiny dirt particles (approaching the size of individual molecules) cling to the coldest parts of the wall because of the loss of energy when they contact those cold surfaces. At those relativistic sizes, then thermal energy becomes kinetic energy and back again easily, so when tiny particles hit a cold wall, they can loose ALL of their kinetic energy to the wall and remain on the wall. Since that happens mostly over the coldest parts of the wall, the dirt collects over the studs, but not between the studs. And, if you give it some time, you can even see exactly where the drywall screws holding the drywall to the studs are located. And, it's all thanks to Brownian Motion and the Twilight zone between Newtonian physics and Quantum physics.
But, rest assured that a Magic Eraser and some elbow grease will eliminate those Brownian particles. You do, however, need to use a Magic Eraser because the size of the particles we're talking about are tiny enough to fit in between the microscopic roughness on even high gloss paints, and so cleaning with a sponge, brush or rag ain't good enough. You gotta use a Magic Eraser which has fibers small enough to clean between the microscopically small bumps on high gloss paints.
Not sure if I addressed the point of your question. On no other building will you find any insulation on the exterior of the wall studs, unless the siding of the building acts as an insulation.
PS: so you know: The ENTIRE PURPOSE behind a moisture barrier or vapour barrier is to prevent warm moist air from getting into the fiberglass insulation. The reason why you want to avoid that is because condensation inside fiberglass insulation reduces it's R value AND insulation works by keeping air stagnant, and therefore wet insulation takes forever to dry out. So, wet insulation in contact with wood studs provides the conditions necessary for the wood rot fungus to start growing on the wet wood. That can lead to wood rot growing on your wall studs behind the wall where you can't do anything about it, and that's often what people talk about when they say a house has "mold".
By using extruded polystyrene foam insulation, warm humid air can't get inside it in the first place, and so it doesn't need a vapour barrier to prevent warm humid air from getting inside it and causing all the problems that occur with fiberglass insulation when that happens. If warm moist air penetrates through a gap between the foam insulation and the wood stud, it might form condensation, but that condensation will dry out come spring or summer, and won't cause any harm. Remember, it's the nature of fiberglass insulation in keeping air stagnant that prevents that condensation from drying out. Condensation outside of fiberglass insulation dries out fine.
Re: the outside of the studs: It's true that the outsides of the studs will be exposed to temperature and humidity changes that occur outdoors, but the bare wall studs in every unfinished garage in North America are exposed to the same environmental changes. Your wall studs will last just as long as the studs in any unfinished garage in Detroit, which, provided the roof don't leak or the garage burn down, will be as long as the wall studs in any structure, finished or not.
also do i cut the foam to fit tightly in between the beams and foam on the face of it? or do i cut it slightly smaller and leave a gap and fill in the gap with the foam?
By "beams" do you mean wall studs?
I don't think it matters much. If it were me, I'd cut as close as I can without cutting the slab too large, and then secure it in place with door hanging shims wedged between the foam slab and the studs and then caulked around the perimeter of the slab with expanding foam. Once that foam cured, I'd pull the shims and cut the expanding foam off flush with the front of the studs. I might fill in where the shims were too, just to be obsessive/compulsive/neurotic, er, I mean a perfectionist.
Now i need to replace it from the inside which is technically impossible since there are wall ties holding up the brick veneer.
That part I don't understand. I can't imagine a wooden stud wall supporting the weight of a brick wall. I expect what you're referring to as "wall ties" were simply metal strips fastened to the studs so that the brick layers could set the brick wall a uniform distance from the wall studs. If that's the case, those ties don't hold up anything. There has to be a steel lintel under that brick wall to support it. STEEL or a short thick slab of solid stone or reinforced concrete are the ONLY things strong enough to support the weight of a brick or concrete block wall. Don't even daydream that a wood stud wall could ever support the weight of a brick wall.
Those things between the brick wall and the wood stud wall are there for some other purpose than supporting the brick wall.