According to
Wikipedia, DVR-MS consists of standard mpeg2+mp2/ac3 streams in a proprietary container format with some extra metadata added. Most of the solutions they offer appear to be Windows only, but they do mention vlc at the end, which is available for Linux. It should be possible to play and/or extract the video to a regular mpeg container with it.
It also mentions ffmpeg, but since it also refers to directshow in relation to it, they're probably talking about the Windows version only. You might see if you can get it to play with ffmplay though. If it plays, then you should also be able to extract the streams and reformat them.
Failing that, it might be possible to run one of the Windows options under wine, or set up a Windows installation in a virtual machine.
This is just another proof that when it comes to interoperability, you need to stay as far away from Microsoft as possible.