OK, I checked out the free preview at my mother's house today (Comcast, Sacramento). I only checked the early games. There was one game in HD (NY vs. Det.). Of course, they only have one, (maybe two after hockey season) HD channels available. Of the games in SD, all but two were in 16:9 within the 4:3 box, i.e., black bars all around. Certainly one could zoom the picture, but that wouldn't help the resolution. I imagine most ball clubs are broadcasting this way for legacy analog TVs, but is there any work around to this?
Honestly, on any cable system doing it this way (apparently most, since they don't have enough HD capacity) I wouldn't even consider MLB EI. Of course, I'm a mlb.tv user, and I prefer the flexibility (home/away feeds, using home/away radio feeds for audio, even the "park" audio feature at times) of mlb.tv, so it's no problem for me.