Do you know by any chance if it was just a local campaign or a national?
I'm pretty sure Zurich and Geneva are the 2 biggest cities in Switzerland anyway. Even if it's just Zurich, that's pretty good exposure, there must be 10's of millions of tourists and other foreigners passing through Zurich every year, many of whom using the trams.
With Zurich's popularity in Switzerland it might be a national campaign that initially done to most visited city in Switzerland with no more than 20 million tourist each year we can totally say that it is made to influence not just the people from that city. I'm pretty sure about it coz if they did not, they could have done it to their capital city which is Bern. But if I were the passenger on that tram, there is no chance I would be paying in bitcoin.