I would just ask the landlord to take it up with the neighbours- rather than fight it out, as it can become unpleasant.
Mind you, we had the reverse situation at our last house in the UK. It was a 1920s house with a large garden, with a paddock at the back that belonged to our neighbour, with a covenant on it stating he could not build. But he sold the land to a builder and we ere unable to make the covenant hold, as it was old with 3 owners in-between. We were able to play around with the plans for the development - insisting that next door would be a bungalow with nor permission for raising the roof or adding windows at a later stage. We were not too worried as we had a very tall and old mixed hedge in-between, with lilac, elderberry, rowan, berberis and mock-orange and a fence behind.
The elderly couple who bought the bungalow started complaining right after they moved- writing 10 page letters (the kind with no punctuations- just ranting) complaining that said hedge was taking away their light. I took flowers over and had a good chat, and explained that the hedge was there for a very long time, was protected by law as being over 50 years and mixed, and was there a long time before they came. EG it was there on the day they first came to see the bungalow, on the day they came for second visit, on the day they signed the contract, on the day they moved. Politely and quietly explaining that we certainly loved our privacy and were not so keen on houses being built- but that they could cut anything over-hanging on their side.
Mrs then said that they bought that particular bungalow because it was much cheaper (but exactly the same) as the others. Yes, I politely replied, and there was a good reason why. She even phoned several times to say I had to go and collect 'my' snails and slugs from her patio. I asked how she knew they were mine and her reply was 'you are the one with the hedge, so they must be yours'. Never lost my cool- but honestly!