So, I'm seeing a little confusion on the gate-redirect thing. That was first seen in "Solitudes," and becomes a fairly common trick later on in the show. The way it works is, you overcharge the originating gate, which causes the connection to jump from the destination to the closest other Stargate to the destination. When they set off the bomb in "A Matter of Time," the wormhole (which was being "sent" from Earth, not to Earth) overcharged, and jumped from the black hole planet's gate to the next closest gate to it (which they mentioned, P3X-whatever). Since Earth was no longer connected to a black hole, they could shut down the gate normally (apparently after sending a MALP and figuring out where the connection jumped to). Abydos and the Beta Gate are completely uninvolved, since they're the closest gates to the SGC, and that end of the wormhole didn't move. From the perspective of the poor bastards on the Black Hole planet, the gate just shut down.
You can only use the overcharge-redirect on outgoing wormholes, so, like, when Apophis was being an asshole at the beginning of the series and tying up the SGC gate and throwing rocks (or bodies) at the iris, SG-1 couldn't have set off a bomb from their end to break the connection.
Could be one of those safety features on the DHD they keep mentioning; once the Black Hole planet's gate understood what was happening, it cut the connection.
You can only use the overcharge-redirect on outgoing wormholes, so, like, when Apophis was being an asshole at the beginning of the series and tying up the SGC gate and throwing rocks (or bodies) at the iris, SG-1 couldn't have set off a bomb from their end to break the connection.
I always thought it was a bit of a contrivance that the episode got them to change from an incoming wormhole (the one SG-10 dialed) to an outgoing one that the SGC had a little bit of influence over. It's equally plausible that SG-10's wormhole would've remained open the entire time. That would've been "game over" ... the SGC couldn't have done a thing to save themselves.
Could be one of those safety features on the DHD they keep mentioning; once the Black Hole planet's gate understood what was happening, it cut the connection.