That's an interesting question. Section 3121 is brand new and has yet to be really tested to find where its flaws may be. The bill was proposed simply to satisfy lenders that at the time of purchase, there was some mechanism by which the access to a property would be kept passable. Once the sale has gone through, there is little in the law to assure a maintenance agreement will continue to function. I've already seen one case where a realtor applied it to a road that is not actually private, but a discontinued road with a public easement. The realtor described the road as being private, with maintenance shared by the abutters. The problem is, only one of the four abutters is a residential property. None of the other three (one of which is the Town and another is a logger) has any interest in repairing the road, which has been damaged by use as an ATV trail.
When the Legislature was considering the bill that became section 3121, they were proposing that only the owners of residential properties would share in the cost of maintenance. I pointed out that ALL owners needed to be included, or a logging operation could get a free ride at the expense of residents. They did change the law to include the owners of all abutting properties, but failed to make a similar correction under enforcement - so a resident only has recourse against other residents, not against a logger.
We also worked hard to make sure section 3121 would allow ANY road maintenance agreement to fulfill the requirements, because there are many situations (especially where there are only a handful of landowners) where an informal or even verbal agreement works fine. (The law accepts "any agreement entered into to determine the share of the cost of reasonable and necessary repairs to and maintenance of the private road...") So the question you raise is whether a non-compliant statutory association could be thrown out, allowing the road to revert to section 3121. The law didn't anticipate that situation, and therefore doesn't make it clear if 3121 would kick in when a prior agreement breaks down.
According to section 3101, a statutory road association continues to exist "until the association is dissolved by a majority vote of its members." But if a road association fails to perform as required by the law, there doesn't seem to be any mechanism for determining that it cannot continue to operate, other than a vote of the members.
I would love to see attorneys and legislators consider your situation and see what can be done to tie up the loose ends in the law.