Presuming that he was meaning a
TAWS or
GPWS rather than
TCAS, they rely on a database of heights of obstacles / terrain. Since this building isn't on any maps yet they wouldn't be any use in this scenario. They aren't going to react to NOTAMs.
Although they are available for helicopters, I'd be very surprised if one was fitted. Flying through London I suspect there would be many false positives - to such an extent a pilot may well turn it off anyway.