So my sequence would be something like:
Select 1st obj - RMB - verts
Shift select 2nd obj - Shift RMB - verts
Then drag select. (don't have maya here so I can't recall if holding Shift on the RMB for the 2nd is necessary). Hope that helps. I use 2009.

When I get home I'll look into it more if you haven't found a solution.