[AlexandrB]

I don't think there's a way to do this without casting something to connect the pre-fab to the surrounding concrete sidewalk. Like how do you precisely cut out the existing curb so the prefab just fits (including elevation/slope) without excessive gaps or something? And if you're pouring concrete anyway, might as well pour the curb itself.

[lstodd]

With prefabs you first dig up both road and sidewalk, set up pre-cut granite curbs (kerbs?) on a mild concrete foundation (negates sinking completely), then repour and repave sidewalk and road. Lasts many years in -20C winters +35C summers climate.