Sky is using the Philips RC6 protocol. At least, everything I'm reading says that they are using it, but there must be something subtly odd about how they are using it. I believe that they may not be using the "toggle" feature of the protocol, but it is also possible that they are using it in a way I don't currently understand... The fact that some commands can sometimes work is odd. (And I have one report from a Tata Sky user that the protocol is working fine for them...)

So I'm still trying to put together more information on exactly what is going on with these receivers. It'll just take some time -- I'm sure other universal remotes are working just fine with Sky, I just need to figure out what they are doing.