Witam,
jesli zrozumiesz to, co tu zaraz napisze, to raczej nie bedziesz miec klopotow :-)
According to the so-called Common European Framework of Reference for Languages (a Council of Europe document) a learner at the B1+ level (i.e. slightly lower than FCE) 'can follow a lecture or talk within his/her own field, provided the subject matter is familiar and the presentation straightforward and clearly structured'.
And that seems to be the point - understanding higher maths even in one's native language is rather difficult for many people (of course maybe it's easy for you), and the English scientific terminology doesn't really add much to this difficulty (especially that this terminology is usually equally new for all students). And as for grammar, Simple Present is usually enough, as science consists mostly of general truths, doesn't it?
Moreover, the command of English isn't an important criterion in the admission procedures (your matura results in maths/physics count much more). Nor is it in the choice of lecturers, for that matter (I mean they do know English, but their professional expertise is more important).
To sum up, I think that such studies are (linguistically, of course) nothing even remotely comparable with English Philology, and that they're also much easier than engineering studies at British/American universities.
Disclaimer: I'm not, and have never been, such a student (not in Poland, at least), so you might want to ask several of them as well.
Hope that helped,
regards,
vindex