UPS in my neighborhood has done something similar in Christmases past--they have trucks bringing in bulk and bicycle delivery doing house by house. I didn't notice it this year; I don't know if it was a failed experiment or if I just missed seeing them.
War is Boring has an interesting post about using unmanned aircraft as a weapon-truck wing-man instead of an independent operator: https://medium.com/war-is-boring/64b87d155545
A computer can know exactly where the trucks are and when they will be in the vicinity. The delivery time can be fairly accurately estimated on the spot.
In an urban environment, bikes could do the last mile, with the robots delivered to pre-designated drop off points. A predetermined location would be easy on the computer.
But I think your idea works better in a suburban zone. The trucks exist and are constantly driving around. It is a question of how to re-prioritize the work on the fly.
I could see something like this working for Pizza Hut though.