The BBC One +1 channel ( to answer the last comment ) could be advantageous for those of us with " only " Freeview if it's going to presumably show the UK schedule rather than the Nations opt outs.
+1 channels were created because capacity was available and it allowed commercial broadcasters to sell further advertising slots, albeit at a lower rate.
The excuse used about allowing people to watch more programmes in an 'ever crowded prime time schedule' really doesn't wash since the mass adoption of VCRs in the 1980s and even less so since that of the PVR in the 2000s.
Nobody felt the need for a +1 channel in 1985, and I don't think they are really relevant now to the majority of the population.
BBC One+1 will be rather pointless given the vast number of opportunities for people to watch repeated programmes, on iPlayer, or recorded on a PVR. In view of the fact that they have no commercial advantage in being able to sell advertising slots, it's probably the worst time to suggest such a channel to the public.
If the BBC want to save money by closing BBC Three then so be it, but there is little point in replacing it with BBC One+1 and HD option. Just give up the transponder space and have done with it, don't try to suggest that anyone NEEDS a +1 channel.