This happens more than you think. I know of a situation where an owner was going to rent his property to people even though he had been served a notice of default. Then, when he finally lost the property on June 28, he promptly asked the tenants for rent for August. They came to me to ask for help. Now they are in court.
Sometimes it is the person who has lost the property that continues to live there until the bank evicts them and sometimes it is an unsuspecting tenant. Either way, banks are sitting on more and more inventory and so this is happening more and more.
Trying to find out who is responsible at B of A is next to impossible. You would probably get someone fresh out of training that has no idea what the 300 files on his desk need. And, if you get an experienced person, many times they are on edge because the bulk of their calls are angry homeowners.
The advice below is pretty good. You might want to encourage your mom to do a little digging though. If there is a noise ordinance in Studio City, she might want to check the specifics. The neighbors may not be violating the ordinance if it even exists. Also, you might want to call an agent to double check that B of A actually owns the property. Some of these were originally done by the bank but then bundled and sold to investors. The most accurate place to check is the city offices off Van Nuys up around Victory.
If they do own it, chances are that B of A will sit on the property for an indefinite time, perhaps a few years. Sorry. I wish I had better news.