if I was to edit a short film on premier pro on a PC laptop, would there be any possible way of then bringing the .prproj file (along with the capture, rendering files etc) onto the mac, and then continueing to edit the project with Final Cut Pro?

Not really. You will have to purchase an application called Automatic Duck, that will do the conversion for you.

What you maybe could do is export the edit you already have as an AVI and import that in Final Cut.
Other then that... I think other people could answer that better than me.