I could swear that I made a post here around the time Telstar 12 Vantage launched in late 2015 that one day it might carry the BBC Satback transponder thanks to its "North Sea" beam - I'm just around eight years or so early!
I suspect given the talk on this thread around six months ago about Intelsat 901 rumoured to be on its last legs electronically, plus it looks like Intelsat have told renters of capacity on the satellite that there's not going to be a replacement on 27.5W once 901 is out of service, is the reason we're likely seeing the BBC Satback service being transferred over to 15W. The only other Ku Band "broadcasts" on 901 are radio feeds for some Irish (North & South) radio broadcasters & it'll be interesting to see if they too will end up on 15W or somewhere else in the sky.
As for the SNR readings some posters are getting here - I'm currently testing out a Technosat TM5402 Mk4 and the Satback transponder is hitting 83% on the quality scale, far better than the EXRN & ESPN feeds at 60% each in wet conditions at the moment - I suspect the monster data transponder on the Mid-Mediterranean beam might be raising the noise floor for those more south & east from where I am located (County Tyrone, Northern Ireland).
Edit: forgot to mention, I'm receiving 15W using an LNB 7 degrees west offset from an 80cm dish that is aimed at 22W.