Tried to find out if you've already got a Maya viewport TF2 shader but couldn't find anything here on it. Anyways, I created one not that long ago and figured I would share it with you. Maybe someone will find it useful. Please do share any feedback. Cheers!Download it here
If you're unfamiliar with working with ShaderFX shaders first make sure you are using DX11 in the viewport (Preferences->Display). Then create a new ShaderFX material, open the ShaderFX editor and use File->Import Graph.