Hopefully someone with current procedural knowledge will pipe-up and confirm the measures are in place but,
AFAIK, when cranes reach a certain height the developer must notify the borough who then notify the CAA who in turn publish a NOTAM.
However, in practice .. when one is flying within a narrow corridor and there are multiple obstructions one really ought to be in unquestionable VMC and, crucially, alert. (Easy to say with hindsight I know).