Do they air live on the East Coast? Are the studio adjacent? I assume yes to both, especially the latter because Tony appears on both.
Listening to Tony Kornheiser’s radio show suggests that while they may frequently tape PTI very close to air time it isn’t actually live. (In today’s show he mentioned having to do an unusual number of retails with Bill Simmons yesterday.)
I haven’t watched either in a while (damn my lack of cable!), but I was always under the impression that Five Good Minutes was taped while the rest of both shows is live.
Funny this question comes up now–I noticed something today that directly speaks to the answer.
I was watching PTI today, and during one of those interludes they intersperse among the commercials, they showed a high, wide-angle POV shot of the set. In the top corner of the screen, you could see what looked very much like part of the ATH set. Based on that, I’m guessing that both shows are filmed in the same studio–the PTI set on one side of the space, the ATH set on the other half, with the cameras located right in the middle. They record ATH, then swing the cameras around 180º to shoot PTI. Hence, Tony Reali doesn’t need to go far to switch from one show to the other–he just moves to the other side of the room.
I don’t know if they’re live or not, though they do seem to be on top of fairly late-breaking stories most of the time. I’m guessing Justin is right, that Five Good Minutes is taped, and the rest of it is live. The “toss” to SportsCenter at the end of PTI seems to happen in real time, though perhaps they’re just smooth with it.
Sheesh, I’m startled to think the fine denizens of the US of A are still listening to a 1960s BBC radio comedy show? 
Its a quixotic world…
They are both filmed at ABC studios in Washington DC. According to this, Around The Horn is taped around 1pm everyday. I would imagine PTI is taped as well, but likely closer to airtime. I have seen them miss topics that are happening as they air, but written about in the crawl at the bottom of the screen. Even if they are live, there is likely a significant delay to deal with issues as they arise. They often have guests via satellite, and to do that without any delay would be stupid.