True. Eastern Oregon towns like Ontario are in the mountain time zone. They receive Boise TV stations, and for the most part are in earshot of Boise radio stations. Eastern Oregon and far Eastern Nevada are the only Pacific time zone States that have parts that are on mountain time.
However, the reasons are different. Ontario is considered part of the Boise metro, unofficially. Wendover, Utah and Jackpot, Nevada are casino towns, and prefer to operate on the time that most of their consumers observe, which is mountain. It can be confusing, but just look to where the consumers are from and you can guess, with some accuracy, the time zone that is observed. Sometimes it gets funny with check-out times at the casinos.