2nm MRS should be getting to V2 maturity in SEASR, not sure of the progress as I'm not directly involved. V2 is the feasbility stage, so effectively to develop a mature concept only.
I know that the project had identified technical and operational issues, among which, I assume, is the currency (update rate) of the surveillance picture. I assume also that the solution to this is muti-static and/or multi-lat. There's a lot of RF energy out there reflecting off aircraft.
edit: cross posted with eglnyt