Couple of things to keep in mind here.
None of these organizations own their own fleets of tow trucks. They all sign contracts with various towing companies to provide service for them. In some parts of the country, they may have a lot of towing companies signed up, in more sparsely populated parts of the country, there may be few, or even none.
Legally, a big old Class A Motorhome or Bus Conversion, when hooked to the back of a tow truck, becomes the equivalent of a tractor trailer. So it not only requires a bigger, heavier tow truck, the driver has to have a Class A Commercial Driver's License. There's a lot fewer of such companies around than there are of towing companies that can tow your car or van.
Any of the Roadside Assistance programs will use their call list of contracted towing companies. If they can't find someone on that list, NONE of them are going to break out the yellow pages and start calling other towing companies for you. They'll all tell you the same thing, find your own tow truck, send us the bill, and we'll reimburse you. (Up to the limits of your agreement. Read the fine print.)
All that said, you should definitely ditch AAA. Apparently, AAA is not really a single organization, but rather a confederation of state automobile clubs, not all of whom offer or support RV service. I've seen lots of posts on these forums of people who, say, got an RV plan through the TX AAA only to find that the MA AAA wouldn't help them when they broke down in MA.
I'd look at CoachNet, Good Sam, and Escappee's and carefully compare the fine print in all their plans before choosing.
For instance, if you're on the Alaska Highway and you break down somewhere with no cell coverage and have to sit there until the Mounties come along and call a tow truck for you with their radio, are you still covered for re-imbursement even though you didn't call in to them first?
