Gflyer, I did exactly what you are talking about. Here is what you have to do. Send or Fax a copy of your elite ff card from another airline and a copy of you statement to: One Pass Service Center, Attn: E. Bell,OA Match. You can get the fax number or the rest of the address of their home page.
I asked for the same thing and they were very happy to do it. They will do it one time only and will credit you with whatever level you had in another program. Try it. It makes sense for them. I did it and have switched all my business to Continental since. Good luck!