I had our corporate travel agent book the following:
CLE-LAX (on CO)
LAX-LIH (United)
LIH-SFO (United)
SFO-CLE (CO)

I was able to use miles (and a copay) to upgrade the United portions- However, when I went to Continental the agent first said that it was united paper and they needed United to let them access the ticket. i waited on hold and when she came back she said that "codeshare flights are not eligible for upgrade on Continental". I can't believe that CO cannot upgrade using a copay and miles a segment on their plane.. Any insight would be really appreciated..

Thanks