They are unable to work over 45 hrs per week over a rolling 26 week period, they have to have a minimum 11 hr break between shifts(can be reduced twice a week), the only other industry where hours are as heavily regulated are Airline pilots.
I personally know for a fact some of these guys still get paid when there is no run to do and are guaranteed 10 hrs a day pay for this.
Yes people are undercutting but that is the state of the whole haulage industry not just the petroleum side as ironically FUEL costs are forcing down margins and companies have to be more competitive on there costings and overheads.