Detroit had the same problem with copper wiring in street lights until a few years ago, when they went LED and were able to reduce the size of the conductors and switch to aluminum, reducing the value of stripping them for scrap.

Didn't we already learn (post-WWII US) that aluminum wiring is an unreliable idea?

No. The problem was in the 70s, with single strand solid conductors which were legal for only a few years due to fire hazards. Multi-strand aluminum is still used all the time. The single strand can work itself loose if installed quickly/without proper care due to expansion and contraction, it's not a concern for multi-strand. Single strand is also ok for a dedicated line to a single appliance / load, which is what these lights would be.

There is functioning aluminum wiring all over the place in america, still operational to this day. I just has problems with overheating and catching fire if the load is too big. If you know the load will never change...

Better unreliable wiring than stolen wiring?