since you say there is a regular and consistent travel time to the job, it could likely be argued your travel time is the same amount of time every day. Unless you record the exact travel time and report that, I do not see them being having a problem with the "flat time" for the travel.
but yes, if you are paid hourly, then to properly calculate your wages, they would have to use actual time. Anything over 40 hours does become overtime. When you get into multiple pay scales, it goes beyond my familiarity with the issue. Somewhere along the line both pay scales are considered but how I don't know.
There are a couple folks that post here that are very knowledgeable on these issues. Hopefully they will add some input.

