Does anyone know if it's compatible with other 3D software like Autodesk Maya or 3DS Max?
It's sort of not.
SFM uses the files from TF2, HL etc etc based on their formats. HOWEVER, It will only use the INSTALLED cache files from Source games. So only official updates and content will be usable in SFM.
with that, because 3D software doesnt use sources (or rather, HL's engine), SFM wont recognise that object.
It's a bit hard to explain, what exactly where you planning to do?
You'll have to make your models usable in .mdl format, the format that Source games use. Luckily there are the Wallworm tools for 3DS Max that can be used to quickly convert models into that format, as well as make your textures usable. From there you'll have to install your models and materials into the proper directories: if you've done both of those right, your model should be among the TF2 model directory and usable in SFM.