Foundation waterproofing

I am working on an existing office building with a basement. The basement extends out beyond the face of the building to the street curb line. A pedestrian sidewalk is the roof of the basement in this area. The sidewalk slab sits on 1/2 the wall thickness. The street curb sits on the outer half of the wall thickness. It looks like before they poured the curb they put down about 1/2" thick asphalt to waterproof the joint.

The City is reconstructing the street and wants to remove the curb. The owner is concerned about water leaks into the basement due to disturbing the curb. The City has come back and said they will consider putting a waterproof membrane down before installing the curb.

I have a couple of questions I would like help with. First, I think the right material is a prefab membrane that is laid down on the wall, verses some kind of canned mixture that hardens in place. Would this be a correct assumption? Any words of caution of preparation of existing concrete for the membrane application?

Second, I have a question about what material might be best. You see the joint is a 'Z' shape. The foundation wall is vertical till you reach the top. Then you go horizontal the width of the curb, then you go vertical again to the top of the slab. It is like a brick shelf, only for the curb. I know bends will be weak points. Any suggestions for the best way to do this?

Third, usually there is a protection board on top of a membrane. I am wondering what is best to do here. There will be differential movement between the curb and the walk slab/foundation wall. Should there be some kind of protection board that wraps horizontally under the curb and then vertically between the curb and the slab?

Fourth, what kind of warranty should te building owner ask for?

My gut feeling is to leave the curb alone since there presently is little leakage. The City is pushing to replace the curb so it matches the rest of the project.

I appreciate any helpful suggests I can get!

Thanks!

Rich