It actually is possible, if you create a dummy Eclipse project and designate the git repository at the workspace root (.git directory at same level as all projects in the workspace). This way when you make commits from this project, all projects in the workspace are its members and you can keep the members themselves connected to cvs.
You can create such repository by first creating the dummy project, and (Team->Share) sharing it via git using the Configure Git Repository dialog. Select “Use or create repository in parent folder” and explicitly remove the project folder from the "Create Repository" line after checking (checkbox) the project from the list of available projects.
After pressing "Create Repository" the project directory suffix will reappear, but remove it again before pressing Finish. In my version of Eclipse pressing Finish will hang, and I must terminate Eclipse to restart it.
After restarting the dummy project can be used to Commit files in all the other projects while the other projects remain connected to cvs.
Screenshot of “Use or create repository in parent folder” view when pathname has been entered by pressing "Create Repository" and then (corrected again before pressing) Finish.