I think this is probably more likely to be on COM 6 (Mux D), as that is currently carrying 14 SDTV streams compared to 16 on COM 5 (Mux C). Not altogether unexpected news, and we can only assume there might be another slot available in future.
I wouldn't be surprised if the winning channel is placed on LCN24 (outside of Scotland) to fill the gap, or if BBC move BBC FOUR to 24 nationwide, and the new service gets the LCN9 slot, which would be very hotly contested if so.
Whatever it is, it won't get channel 24 as the LCN policy has ruled out giving the same number to different channels (with the exception of Local TV services). The BBC won't move Four off 9, either, as it's entitled to a low
EPG position as a PSB channel.
More than likely it will go to a broadcaster already on Freeview (in which case they could use one of their existing numbers), or possibly a certain news channel, which would go in the 230s anyway.