They'll obviously be able to use the same file formats, but the mesh is a bit harder.
Someone once requested the ingram mech model be ported. I looked into it and found the original UT model had been saved in an .int file, which pretty much made it impossible. In that case your only option is to beg the original author and hope he still has the raw files. If it's saved in .u format, you can't just convert them, but you might be able to use WOTGreal to extract the mesh to an editible file format, then import it into max for attaching to the bones. It all depends on what the file format was for UT.
I really do wish everyone would try to contact the original authors before asking strangers to make ports.
Someone has already done a few of the old models. I know the metal guard and one other group (the one cliffy called gay, I forget the name) was transfered, you'll have to search at the atari forums for them.