1) Why is the route sign in Russian?
2) Is there that much demand for multiple unit trams in Schwerin now? Having those in a city with a population of 100000 is just amazing!

This is not Russian, but Ukrainian.
I do not think that further explanation is needed, especially as I don't want to cross the 'red line'.
If it may seem like a pointless measure for trams (anyone can read a number), it should be considered that this also applies to buses.
There I have read other things, such as "departs in 5 minutes", "not in service", "journey limited to..." etc. So here the transliteration is useful, because these are not evident messages, unlike the name of an end point. It's also possible that certain bus lines in the same direction may have different end points, and this can also be useful here.