Neighbours tree roots blocking our sewer

Hello again!

The TWO sewer lines from our building to the main sewer trunk is becoming more and more compromised by the roots from a large fig tree on the neighbouring property. We have been advised by the plumber that the clay pipes need to be replaced with PVC to eliminate the problem. This is a costly job as the parking area will have to be carved up to do it.

My question is… who is financially responsible for this repair?

The tree is very large and quite old so it could have been there when the blocks were built in the 1960s. We have been advised to approach council about the problem. Does the council have responsibility/ liability for big trees inside a property boundary? Does the neighbouring OC have any liability?

I suspect it would be prudent for us to approach the neighbouring OC directly (that’s my current plan) That way we can approach council with a united front (fingers crossed) if appropriate. 

Anyone got an opinion??

Thx