some ukrainian drivers are now working in poland, could this be a plus?
In showing that foreigners are accepted as drivers yes.
it's very similar to polish so it would be "easy" to learn
Look at it the other way, any Ukrainian you know would help you learn Polish very quickly.
But beware about mixing slavic languages. For non-native speakers, a second or third slavic language is liable to interfere with those you already know in weird and unpredictable ways.
This is unlike Romance languages where knowledge of one mostly helps with others and where interference (dropping Italian words into Spanish or vice versa) doesn't make you sound crazy.
Especially Polish and Ukrainian are just similar enough and just far enough apart that it will be tricky to keep them apart but randomly using words from one in the other will sound.... very weird.
Learn Polish (not so hard if you know some Ukrainian) and start contacting the mass transit authorities in cities with streetcar networks, see here for the larger cities with trams to enquire about feasability of your plan:
en.wikipedia.org/wiki/Transport_in_Poland#Tram
nb. Very often in Poland the first answer to any request or enquiry is "No." Don't take that too seriously... often it means "I'm busy now" or "Let me think about it" or "Convince me".... persistence pays off!