Need a new curb trap

So i found out that i may need a new curb trap which sucks but i also noticed that my neighbors roof drains into my downspout. I live in philly and we have a common sewer line so my down spout goes right into my sewer line that leads out to the street. I was wondering if i have to share the downspout with my neighbor. I dont know how it works with townhomes but i dont like that all his runoff goes through my system.

backstory
How i found out i had a broken curb trap is when it started to rain hard last week water rushed in through a hole in my basement wall and i mean a lot of water. then a few days later we noticed all the water in the house started coming through that hole. so the water is draining out of the house then through the broken trap then back towards the house. so now i will have to spend 2-8 grand to have it fixed.