Yes, Ray is correct. The whole reason for the passage of 23 MRS section 3121 is so that a lender could be sure a property being sold would remain accessible. So where there is a private road with any form of road association or maintenance agreement, no matter how informal, that provides assurance that the access will be maintained. Section 3121 was intended to kick in ONLY when there is no sort of arrangement for seeing that the road gets needed maintenance.
Unfortunately, as often happens with new legislation, there are a few bugs that still need to be worked out. The bill as originally presented would have divided the cost of maintenance only between owners of residential properties. That meant that if there was a business that did heavy trucking over the road, (for example if the road served a wood lot, lumber mill, or gravel pit,) the owners of that business would have no obligation to share in the cost of maintenance even though their use of the road would likely cause much more damage than residential use.
When that flaw was pointed out, the bill was re-worded to assure that all property owners would share in the cost of maintenance. Unfortunately, somewhere along the line the paragraph on enforcement got changed back so it only allows a residential property owner to sue another residential property owner who does not pay their share. There is no method of enforcing payment by the owner of a non-residential property.
But to your question directly, if there is a road association in place, section 3121 does not apply, and therefore there is no conflict.