You have good eye's
The MG1 "Rijndam Infra" inspection train is not part of Beta 3.11, as I deem the quality not high enough for public release.
It is just two interlaced MG2 carriages into one, with the interior stripped out, but the 'back ends' of the two parts are still clearly visible trough the windows. I still use it (even earlier today) for work on the line; in the editor, taking a metro (and using time acceleration) can be the fastest and most convenient to get to other stations on the same line.
You can see part of it in the screenshot as the skin is simply stored on my computer as one of the repaintable MG2's, so the colourscheme also tends to pop-up when I load an activity, and the repaintable MG2's appear