Lots of people have Macs...the IT department does recommend PCs, because the hospital computer system you use for clinical year does not get along with Mac products at all. Also, IT is able to fairly easily work on PCs if they go haywire, which I've experienced before -- my laptop harddrive crashed (luckily under warranty), and I was able to get the new parts in the mail and drop off the laptop and all its bits at the IT office in the vet school and they had it fixed for me by the end of the day.
That being said, I have plenty of Apple-obsessed classmates that would rather use school computers for anything incompatible than bend to getting a PC, and that's fine too. There's absolutely no requirement when it comes to type of computer. You could take notes on a typewriter for all anyone cares.