Here are some tips for anyone looking at remote control extenders. This is based on what I've read on AT&T U-verse forums over the last couple of years. U-verse uses the same hardware and software and has over 2 million subs, so it's a good resource for more unusual situations.
The VIP1200 series uses a carrier frequency of around 60 KHz while many IR extenders only repeat frequencies in the 40 KHz range. One product that users have reported success with is the
Hot Link Pro.
I haven't tried a remote extender personally.
Another possibility is an RF remote that AT&T sells as an option, although it may be hard to get your hands on one unless you know someone that lives in the U.S. I've heard a rumour that MTS will also be selling an RF remote.