I've heard that some stations are broadcasting HD LOCALLY in 1080P, but only LOCALLY. You have to be 'line of sight' to recieve their uncompressed signal. It may be that this is true or it may be that they are just tramsmitting an uncompressed signal (no MPEG2 or MPEG4 etc). I can't be really certain as I have no firsthand experience with this kind of thing, I don't think I want to bother setting up an antenna for Global or CBC to find out, they don't have particularly interesting programming and I don't relish a lightning lure on my roof.
Another great part of Optik, no antenna and built in lightning protection, oh and snow wont build up and block your Opik signal either

.
Once the HD signal is bundled up for transmission over satellite relay to providers such as TELUS or SHAW or Bell Xpressview etc, its reduced to 720P to save bandwidth. 1080P bandwidth is just not doable currently for satellite uplink there isn't the room required.
The providers then decide what type of data compression they will apply to the signal they receive from the networks, in the case of Optik its MPEG4, this further reduces bandwidth, and this is how the signal is delivered to the STB. Non HD signals are transmitted at 480i with MPEG4 compression used in the case of Optik. The STB is capable of changing the resolution of the HD signal to either 1080i or 720P for HD TVs or 480i for non HD TV sets. The SD channels remain 480i as far as I know, the STB doesn't upscale them.