Is it possible to unlock a Bell Blackberry and use Virgin Mobile?

I have my cousin's old blackberry and she was with Bell. Im with Virgin and my cell is a **** box. I have a year left in my contract and I will not waste money on a new blackberry if I want to switch providers in the future anyway. SO if I unlocked her blackberry, will I have an issue using it with virgin?? I live in CANADA and if it helps, I wouldn't upgrade to a data plan (no Internet, no bbm, nothing like that).. I would keep my old regular phone plan-I just need a new phone.