Of course anything's possible with those tools I would suppose, but I think my worry would be if something went wrong and I needed support. It wouldn't surprise me if neither company were anxious to support a set up such as you describe.
Have you thought about perhaps using both tools but not trying to connect them?
Yes, tried them all.
I couldn't get the commandline to work through TD.
We host a range of tools that are chosen for different reasons, by different project groups, for [wait for it] different tasks.
WinRunner is extensively used, but occasionally it just won't do what is required for a piece of software. Having QARun around is handy in these cases.
e.g. A project wanted to start using TD and had all their tests in Word. The TD Word import couldn't handle the sheer volume of numbers. Eventually we exported the tests to CSV and got QARun to pump the tests in, directly through the front end. Worked a treat.