The NEC requires "high legs" to be marked with orange (orange is also used in 480/277 panels). If you ever see orange in a 208/240 panel it should raise a red flag.
The other place "high" or wild leg services are found are in places that are mainly 120 volt loads, but need or want 3 phase for AC/air handling. The POCO can do a wild leg with 2 transformers instead of 3, saving them money (sometimes cost that is passed on to the customer at the time of install-so its not always the POCO being cheap).
One of the odd/annoying things is that POCO's don't play by the NEC-they use the NESC. In my area, the POCO uses blue/yellow/red to mark 480-electricians use brown/orange/yellow. The NEC requires high leg to be "B" phase, I think the POCO usually runs their equipment with it on the "C" phase. Obviously an easy place for a mistake/miscommunication to happen.