I have read this entire thread and the links provided, and I'm not here to state a position or take sides. However, I would like to make a couple of personal observations that may or may not have anything to do with the actual legalities of this issue. First of all my previous and current coaches were/are two axle, but both well over 26,000 lbs.
Things may have changed but about seven years ago I fueled at the truck pumps at Love's in Yuma. When I went inside to pay the cashier asked if I was the one driving the motor home. I told her yes, and she said she needed to calculate a tax credit off of my charges. When I asked her why, she told me because I was not a commercial vehicle I didn't have to pay the higher tax rate (I don't remember any of the numbers), but I did pay a reduce bill.
Earlier this year I fueled at the PFJ in Kingman in the RV lane (so I could get my CC 5% rebate). While I will admit I didn't read any of the small print posted on the pump (I never do), one would think if I shouldn't have used that pump because of my weight, that PFJ would have a large sign posted informing drivers of the axle and/or weight restriction.
It would seem to me if coaches weighing >26,000 lbs were not legally supposed to be fueling in the RV lanes, then the AZDOT enforcement officials would be on site making a ton of money for the state.