[...]It is also too low to drive under with a truck to spray the path with salt, cleaning and do other maintenance.
There are small "trucks" available to salt and to clean the path if neccessary. These are already regularly used where i live to salt cycle paths that are not directly adjacent to roads. Those would easily fit under this canopy.
Regarding birds: Why would you as a bird walk on a slippery - and in summer also hot - surface where you can't find anything to eat, if there is a nice lawn nearby?
Sure, some bird poop and other dirt will accumulate, as on almost every other solar panel. How much effect that has would be interesting to observe. On my roof system dirt has no noticable effect on the output of the system, and the panels are visibly dirty.
I find it's functional but looks so ugly, way too many poles (unless there is expected significant snow load) and where does the rainwater drain? As a bird, I'd like to walk around on it and poop
There is a small ditch on the left side. On the left side of the canopy there is also what looks like a raingutter, evident when you compare the two sides. Now, how they get the water down i don't know. The poles are likely hollow, maybe they use them directly instead of additional downpipes?
And regarding the number of poles, well, i think thats a german thing, especially if this was publicly funded. Some "paper warrior" somewhere likely took the most extreme snow in the last whatever years, added a nice safety margin to that, and thus calculated the number of poles required. Maybe add a couple more for the case that some are knocked down by an accicent as well. And from the perspective of the architect, this is actually sensible, as there can be personal liability if this thing comes down, but there is no liability if it is ugly
Some months ago, there was a pilotproject for covering an Autobahn with solar, very similar to this covered path. That looked even more overengineered.