There seems to be a move on to expand radar/VHF coverage onto more of the Tango routes. I remember a few years ago Shanwick were asking aircraft to do VHF radio checks with Shannon and Madrid as they proceeded along T9. I'd be confident of being able to contact either Shannon or Madrid on VHF above FL300 at any point on T9 based on the few radio checks I heard. Reliable radar coverage would be harder to achieve I imagine, but with future technology like space based ADSB reception, it probably isn't required.
And recently Santa Maria Radar appear to have expanded coverage on T16, eliminating the requirement of a position report when entering T16 at Navix the last few times I used it. Around 80 miles north of Navix they terminate radar and VHF service.