Apart from the fact that this prototype is very ugly, some limitations come to mind.
- Maintenance without blocking the bike lane. Does this require a separate access road?
- Will this work when any trees are nearby? Falling branches are likely to cause damage and block the sun.
- How does this work when buildings are nearby? You will block all the light? I'm having trouble imaging how this will look good in a more dense area - not the mention the extra width required on the sides of the bike path will be hard to get where space is at a premium (cities).
All this seems to point to a rather limited use case: bike lanes in places with few buildings and few trees, and sufficient spacing around the structure to facilitate maintenance access. That presumably means: in sparse industrial zones near edges of cities (as pictured, I suppose).
Which leads to another question: how many sparse industrial zones in Germany actually have bike 4m wide bike paths?