While I don't use Modo, I'm going to assume that it can manage .fbx files. That's a start when it comes to moving stuff around.
If you're bringing in lightmaps that aren't baked with Beast, then you've got 3 options in order from best to worst:
1) Use Beast.
2) find Unity's legacy lightmapping importer (google Unity Maya lightmapping, should find it)
3) Roll custom lightmaped shaders. Diffuse/spec/normal go into UV0, Lightmaps go into UV2, Unity lightmap math can be found on the forum, basically it's in the 0-8 range, using all 4 channels.
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If you're bringing in lightmaps that aren't baked with Beast, then you've got 3 options in order from best to worst:
1) Use Beast.
2) find Unity's legacy lightmapping importer (google Unity Maya lightmapping, should find it)
3) Roll custom lightmaped shaders. Diffuse/spec/normal go into UV0, Lightmaps go into UV2, Unity lightmap math can be found on the forum, basically it's in the 0-8 range, using all 4 channels.
Although if you import your textures before your mesh, it'll sometimes manage to at least pick the right diffuse textures.
Unity's lightmaps are compressed to RGBM so you'll have to roll your own shader to use custom baked lightmaps.
I'm not 100% sure how modo sets the order of it's UVs for exporting, I think it's by order of creation.