Setting up rEFIt-based tripple boot system on a Mac with a pre-existing Boot Camp installation
I've just decided to go ahead with it and see what happens and rEFIt successfully picks up the Windows 7 partition as desired.

Following the Lifehacker guide to triple booting, there's a section that says


  If you've already installed Windows using Boot Camp, though, that's
  fine—just ignore the Windows parts of this step