The airline obligation under EU directive 261 is:
1) to offer you a choice between reimbursement or rerouting at the earliest possibility.
2) a compensation of EUR250 unless they claim extraordinary circumstances.

Apparently they did offer you the next flight (evening). They could also have rerouted you via MUC on LH which departs at 6am. After discussion, they replaced your original routing by a BSL-CDG. IMO you should have asked for AF to cover the train/bus cost before accepting the rerouting. It seems a bit odd to claim it after the trip without prior agreement, and the cost is small anyway.
For compensation, they are likely to claim extraordinary circumstances to protect pax safety. As you can see on page 7 of this document, this is a grey area:
http://www.flyertalk.com/forum/air-f...ain-costs.html