Restart/Catchup feature on MSO-issued non-IPTV TiVos

Just this afternoon I noticed that the guide on my RCN-issued TiVo (Arris MG2/DCX900) is displaying the little icons next to shows that indicate the ability to watch them on demand, even if the show wasn't recorded, as illustrated here:
Apparently RCN IPTV customers have the ability to play nearly anything on demand that aired on many channels over the past three days, and it's now been rolled out to TiVo boxes on the traditional CATV network. It seems to work well, but it doesn't allow fast forwarding. Also, the feature is appearing in the TiVo iOS app, but I get an error message when I try to replay a program.