Video surveillance evidence could exonerate you (or not) depending on what it showed but it is probably just as well that Biz A has nothing on tape that they potentially can use to support their claims.
Did Biz A ever report the alleged property damage to the police? Was there an investigation into illegal chemical dumping or vandalism or employee injuries? Anything
at all that Biz A could use to connect you or Biz B to the damage?
Was asked a few years ago if I would sell or rent I refused several times ... they told me in a conversation they could wrap me up indefinitely in a law suit and cripple me financially if I do not let them use my property.
Was anyone around who heard Biz A say the above to you? That would be of benefit to you.
Again, you really need to see an attorney in your area for a personal review. Following is a link to the California Bar Association where you might be able to find direction to a low cost attorney in your area:
http://www.calbar.ca.gov/