They could benefit from the new Freeview rules and get a fairly high channel number. Wouldn't surprise me if they chose to put C5HD on 5 and bump the SD equivalent down the EPG
along with all of their other channels.
That's not allowed yet. The new rules only apply to HD-only channels and, as was clarified by a Digital UK spokesperson today, is only a reservation until such time that a SD/HD substitution is allowed. At that point, the channel's reserved slot becomes its actual slot - it's so that HD-only channels aren't disadvantaged when the HD section is removed and aren't tagged on to the end of the channel list. Remember, many Freeview HD receivers sold in the past 5-6 years would not cope if both the SD and HD version of the channel had the same channel number - one version would get bumped in to the 800s. If they swapped channel number allocations, Freeview SD users would see some of the main PSB channels in the 100s while the commercial SD channels remained in situ and nothing on channels 1-4 ...and that would go against EPG Prominence rules.