Advice on difficult neighbor/tree limbs Q

[Felicia Hamilton]

The city has mandated that all homes be on city sewer, I have an investment property (SFH) that I'm attempting to transfer to city sewer... however, the plumber will have to be on my neighbors' yard by less than 2 feet. My neighbors, a retired elderly couple, are adamant that they NOT be on their property. This is not a manicured lawn, it's on the very edge of her land (not even close to their house). Any disturbance would be rectified. If they weren't home, they could have done the work and they wouldn't have known any better. If we weren't in a state where the likelihood of them having a firearm weren't so high... I would say screw them, and do the work, fix the yard while they scream and holler... but that's not the case. I could cut down a tree to give the plumbers more access and not be on their yard. This will increase my cost about 2k. I'm fine to do it, just to get this city mandated project done... but I'm irked. We've had a VERY FRIENDLY relationship in the past, so I'm really confused by the whole thing. I've even offered to pay them JUST TO HAVE ACCESS TO THE 24 INCHES!

My question - if I cut down the tree and branches/leaves fall on their property... do I have to remove the tree debris, or anything else that may fall on their land?