"That's hilarious. There's always a receptionist with keys to the basement or pabx room that will give up keys without asking questions if you've got an orange vest and a decent looking id card."
That rules out Chorus then. �They can't install anything in a shared building without a 90-day lead time and a mountain of consent paperwork.
Also the procedure for obtaining a roof key is slightly more complex as it usually involves the receptionist first a) checking that you are in a happy, smiling mood and b) cautioning you sternly to "make sure you don't fall off"