It's been the same since 1998 when Sky dropped the Egg logo in favour of 'sky' for corporate reasons and 'SKY' on the channel idents. It's also worth noting that since May 1998 the whole lot of Sky channels haven't rebranded at the same time, where as previously they used to. For instance Sky One was the first channel to drop the egg logo in May 1998, it took until October for the rest of the channels to rebrand. Same again in 2002 when the Sky font changed to the current one, it took almost a year to be fully implemented.
Although it's been going for over a year now, Sky's 1-3, Real Lives and Arts all have the lowercase logo where as News, Movies and Sports use the uppercase logo's, even though these channels have all had rebrands within the last couple of years.