Randalstown is pretty much gone. I know a daughter of the rav who used to have the shul there, and there are hardly any frum left at all. There are a few frum in Mt. Washington, but not so many, since the area is really expensive. It’s also far from kosher shopping. The Park Heights – Pikesville corridor and the northern extension into Greenspring are where most frum live. If there aren’t shuls already there, or the zoning laws will prohibit turning houses into shuls, then people just won’t move there.
I believe TA is outside the general eruv and mostly only TA faculty live there.