Using r3066 build and pak128:
1) build 110 km/h track, electrify with 110 km/h wires
2) add depot, send a fast (>110 km/h) loco on the track
3) select 160 km/h track and build over previous track
4) observation: train obeys only track max speed, not catenary
Originally reported here: http://forum.simutrans.com/index.php?topic=3931.msg42639#msg42639
should be fixed with revision 3077 in both trunk and stable. thanks for reporting.