I would assume the repositories themselves could be moved. The thing is that they provide additional services beyond just hosting a git repository like issue tracking, wikis, and continuous integration support. Presumably that stuff can't be moved.
When the company I work for moved from Gitorious to GitLab we were able to migrate the git repositories with all their history relatively painlessly. GitLab had an automated process for doing it, but due to reasons apparently the Gitorious side would randomly flake out if you tried to use that. (It had to do with ulimits or something.) However you can still just clone a git repository and push branches from it to a new remote, which is the way I ended up transitioning most of the repositories.
The issue tracking and other features weren't an issue because we weren't using the built-in Gitorious/GitLab support in any case.