Yes, I tested and it works.
Do this:
Imagine your object has three UVs maps.
Duplicate the object until you have three copys of the object (one for each UV map)
In first object delete the second and third uvmap. Select all the faces of the UV and now choose Select inverse in the menu and delete the faces. So your first object has only the faces of the first UVmap.
In the second object delete the firs uvmap and the third uvmap and delete all the faces that are not in the uvmap.
Same for third object: delete first and second uvmap and in the uvmap that remains delete the faces in the object that are not in the uvmap.
So you have three objects and each one has only the faces that are in the uvmap. Each object has only one uvmap. This uvmpa doesn’t need to have the same name.
Now place the cursor in the first object (select the object, shift+S and choose cursor to selected). Now select the second object, shift + S and choose object to cursor. So first and second object are in the same location. Do the same with third object so all the three objects are now in the same location. Now select the three objects and choose join in the menu and you have now only one object and all the uvmaps merged in only one uvmap. You will need now to weld the vertices (remove doubles).
Done!