I tried loading a midi file I had made from a project created in Reaper. It contained tempo changes wich are supposed to be integrated in the midi file. When I load that file in GB, I get no tempo changes. The tempo in GB stays at the default 120bpm. So I guess the answer to my question would be no. But I want to make sure I'm not missing something.
Mac mini, OS X Mountain Lion (10.8.2), Mackie Onyx 820i Firewire Mixer