yeah but google code doesn't use perforce either... so it's possible (not saying likely). I tend to agree with the rails thing...
A more plausible thing for google would be to build a backend for git so they could store git objects, either on bigtable or on GFS. They need this to make the hook into their infrastructure. As soon as that backend is done, they don't need that much work to get a service akin to GitHub.
It doesn't really ring with me that they should want to acquire GitHub.
But the politics of Rails mean that the github guys are unlikely to want to piss off the lighthouse guys by including even the simplest issue tracker.
Instead, I think they don't WANT to do ticket tracking. That's not what github is about. It's a social network built around code. I don't think it's a business oriented project management site.
Also, if someone is going to take the time to go through the code after forking, they might feel like fixing any bugs or handling a few new feature requests while they're at it, especially for small, informal projects.