Some bits of CS are very specific about PhDs, and yes the use the "top school" term.
...but no, like pretty much everyone else they don't define "top school".
I do not speak for UBS, but there is no policy on PhDs that I've ever seen. They see that as evidence of what they are looking for, but not proof, and that cuts either way.
In general there is no "in general"
Different managers like different things. Some hate MFEs, other hire nothing else. Some will only look at PhDs, and there are something like 100 schools in the "top ten".
That's before we get to stuff like some liking Russian and French schools, some equating a DEA to a PhD, and of course the school they went to was a "top school"
However
IlyaKEightSix was being more than a bit optimistic trying to get an entry level quant job anywhere with a BS. The market is divided between those who think you must have a PhD and those who see MS as the base, very few see BS that way.