Sky One has shown this now and it follows on directly from 'Inauguration'. It is a pilot for 'Atlantis', but it isn't an SG-1 'light' episode, it actually features Jack more than the rest of this season put together. There isn't much off-world action except at the start, but it does feature Bra'tac. It also has some light-hearted moments with SG-1 and Hammond off duty at Jack's house.
The spoilers seem to be almost completely correct. Daniel decifers some code and thinks that he has found another of the Ancient devices for receiving their knowledge like the one in 'The Fifth Race'. Hoping that this will lead them to the location of the 'Lost City' they go to a planet to investigate. Their has been one of those Goa'uld probes seen so they take along two other SG teams for back-up.
Just as they find the device, Anubis turns up. Unable to work out how to safely download the information, and not wanting to give it to Anubis, Jack wants to blow it up. Daniel thinks it is their only hope to find the 'Lost City' and wants to put his head in, but instead Jack "I did it again" does. This is why Jack is dying. They cannot contact Thor, who helped save Jack last time.
Hammond is relieved by Dr Weir and meets the President in Washington. Hammond is thinking of retiring, but the President has another unspecified job for him.
Bra'tac arrives saying that Anubis is going to attack Earth in three days time. Anubis thinks that they now have the location of the 'Lost City' and it's powerful weapons at their disposal.
Jack begins saying odd things. Bra'tac and Teal'c return to Chu'lak to gather some help for Earth. Dr Weir stands up to Kinsey