Sort of, but a tunnel network of that type is never going to be able to handle many users, no matter how good the design gets, while improved and safe jetpacks probably could replace most of the cars on the road.
I doubt it, for basically the same reason that electric bicycles are not going to replace most of the cars. They might be great, but are not very nice for long commutes in poor weather (while wearing fancy suits or dresses/skirts).
For jetpacks there is an additional huge problem with safety flying over inhabited areas. Unless the jetpacks are meticulously maintained and inspected, we would see people falling out of the sky on the daily. Taking the maintenance state of most cars as an example, it seems safe to state that it would be infeasible to expect the general population to keep their jetpacks in an acceptable state.
