The guys that ran my waterline usually do all of the local county waterline work, and they used the same materials and methods for me. My line was also 2" PVC, slipjoint. I was expecting them to be very careful about depth, backfill materials and tamping, etc. Nah. Saw the trench, heave in the pipe. If the trench partially filled in with trenching debris before they got the pipe in it, no problem, as long at it was still at least 18" - 24" deep. Backfilled with the sawn rockdust/dirt, pushed in with a dozer, and when completely filled, run over the whole thing a few more times with the dozer. That was it!
But I had several branch lines put in for hydrants, and the lack of good backfilling and tamping caused a problem that they don't usually have when just running continuous straight lines. Several of the branches blew out a slip joint when the line was pressured up. In your case, high pressure and branch lines probably won't be an issue, and you should have no problems.
- Jay