It will probably work, but is not a supported config. You may be killing your warranty / service agreement.
Also, it has to be be the same type of GBIC. Chances are it needs to be an SX GBIC. If your Cisco GBIC is an LX or ZX, this is NOT something you'll want to do (unless the other side is also an LX or ZX -or other type-)
You also want to make sure the GBIC is for the same fiber type (single / multi-mode).
Good Luck
Scott
