There are three main types of truncated domes:
Cast in place concrete
Precast concrete tiles
Glue-on plastic
Iv'e heard that the cast-in-place ones have problems with freeze-thaw spalling that pops the dots off. It could be that a conventional mix wet enough to form the dots is too wet to stand up to winter conditions. Or maybe the workers are adding too much water on-site.
I just saw an article on self-consolidating concrete. It's a high-slump, high strength mix designed to flow around complex reinforcing and eliminate voids without vibrating.
I don't know if anyone has tried it for cast-in-place tactile dots, but it might solve the spalling problem.