Degrees are accepted almost in entirety. Most people do one or two 400 level courses in discrete mathematics/linear algebra and/or a core focus area but mostly it is straight jump to grad studies. And most grad students are TAs/RAs. It is difficult to secure one right away, mostly after one season but a large number of grads here are on the COMSATS faculty development programme fellowship.
You can directly contact grad students here. I can give you their emails.
I really don't know a lot of people here. The Intl Students and Scholars office says that there are 81 Pakistani students (Green Passports) here besides the nearly 200 of Pakistani origins. Of them, I know nearly 30-40.
The grad programs in these fields are very famous and highly ranked, besides being competitive. "Environment" of course can be evaluated in varying degrees depending on social, political, religious and academic interest