I know of a similar situation where 2 gardens are back to back. The gardens form a continuous green space that extends from street to street but there is a fence between the two gardens that neither garden is interested in removing. How did this situation come to be? A few years ago the gardens received city funding to install an in-ground water system. At the time one of the gardens was much more developed and organized than the other. The gardeners from the more developed garden were somehow able to get the water brought in to the less developed garden including the obtrusive above ground unit that contains the shut off and back flow preventer equipment. After this the less developed garden became more organized and decided to keep the water on their side, not wanting to further disrupt their garden to extend the piping to the garden on the other side of the fence. It became a clash of cultures and income levels. The disputants have resisted attempts at mediation and today both are beautiful gardens physically but the ugly dispute still continues below the surface beauty. One garden has a water system and the other uses the fire hydrant.
I can't say that I have the answers to resolve these particular situations. It is difficult enough for community gardeners to sustain-ably govern themselves in normal situations but introduce money or valuable equipment to the equation or attempt to take away limited space and the task becomes almost impossible.