r5723 introduces a bug where demolition costs are not calculated correctly in my opinion. Demolition cost should be the same as construction (which was true in 5722) - however now half the cost of a new powerline is added on, so if powerline tunnels cost 1000, and powerlines 350, then powerline tunnel demolition now costs 1175. I'm assuming my code was buggy in another aspect?
This is at least how all other costs from tunnels are calculated in the game. Otherwise removing powerlines from an underground crossing or such would be free. Anyway, not charging for underground can be introduced again.
The cahnge was due to two errors reported on the japanese forum: http://forum.japanese.simutrans.com/index.php?board=4.0
Road and rail tunnels cost the same to demolish as they do to build I thought?
No they do not. But they should ...