If the owner of the property agrees it is probably legal. If the owner of the cabling is not a regulated public utility it is probably legal.
If it has been wired by a public utility then you should have some rights to use the wiring. Otherwise all bets are off. Be best to negotiate with the owner of the MDU and run your own wiring if possible. From: Gino Villarini Sent: Monday, January 25, 2016 1:12 PM To: Animal Farm Subject: [AFMUG] Can a provider have exclusive rights to MDU access cabling? A local provider wired a whole business MDU. We are trying to light up a customer on the premises. They are charging ridiculous fees to access the cabling. Is this legal?