The €49 ticket has been a political project, introduced to allow residents to stop driving individual cars. The purpose is (a) to reduce CO2 emissions and (b) to compensate for the price increase of gasoline and diesel because of the Russian attack on Ukraine. Last year, there was an €9 ticket for a couple of months, charging €49 now is still subsidized but more sustainable for the public budget.
The ticket is valid for local transport nationwide and it can be sold by different transport companies, with slightly different rules from state to state. Yet companies in any state should accept tickets issued in any other state. It might be a good idea to ask your local public transport provider about their policy.
Beyond that, there is the Deutsche Bahn, the national rail company. The €49 ticket is valid in their local trains, but not in their long distance trains.
Here, the Bahn website talks about ID documents in conjunction with online tickets. They accept identity cards from EU countries, passports from other countries, and some special cases.
Here, the Bahn website talks about ID documents and list European, Swiss, and Norwegian ID cards. This strongly implies that they read 'European' as EU, whatever the geographical realities.
Here, the Bahn website mentions the physical BC100 card on a page directly linked from the €49 ticket, which looks like nonsense.
My conclusions are:
- The Bahn is still confused how to handle the recent nationwide ticket.
- They mean "EU/EEA identity card or international passport", even if it might be possible to talk an individual conductor into accounting other ID cards.