Not in any officially supported manner.
That said, it doesn't take too much exploring to see that some of the APIs are already present in TFS 2013 already.
For example, if you're using TFS2013.4, try sending a GET to https://{yourserver}/defaultcollection/_apis/git/repositories?api-version=1.0 and see what the result is.
Examples of using the REST API for on-premise, when they do turn up, will be all but identical to the Visual Studio Team Services REST API documentation.
P.S. I'm not sure if the work item APIs are there yet. I get 404's when calling the work item specific API URLs.
UPDATE: TFS2015 has now been released and it includes the full REST APIs from Visual Studio Team Services.
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