I have installed Wine on Slackware 9.1 with good results. I was able to run Trillian, circutmaker, Microsoft Office, and others. I don't see why it wouldn't work with MPLAB (not sure about the loader program though).
Only one way to find out
go download/install wine and see if you can run MPLAB (I would try and run a version installed by your XP installation.
Greg