I believe that all channels will go dark when the UK buyout will be approved, as before if there is more subscribers then the buying price could move up for the sellers under their request (Imagine if they would gain 20% subscribers, definitely Sellers will request an increase on the paying price that generally in such business is related to the numbers of subscribers or a value of the company per subscriber)... it's the usual piracy trick, then once the buying is complete the new security will be completely implemented. At what we can see, they thought it would go quicker the acceptance of the buying and already started to "upgrade" to the more secure system, all boxes SD and HD have the security chip that do the job, also the old SD STB of 1998... it's moving out of the standard DVB Encryption system to their own (like DirecTV uses in USA, that is not DVB Standard).
It happened also with DirecTV, a lot of piracy before the buying and the counter measure was implemented only when the buying from Hughes/GeneralMotors was completed to acquire the new subscribers only when the buyout was completed.
TS
I read an interesting thing. It may be possible that sky were forced to implement the icam on older boxes due to premier league football rights and card sharing was the biggest source of piracy. What that might mean is that they didn't want to do that but had to. So possibly the secrets of icam are to be found in the unsecured boxes software.