Are historical easy_to_borrow values available?

I’m currently backtesting a strategy (outside Alpaca) that I intend to run on Alpaca later.
Is there any way to get historical information on which equities are easy_to_borrow/shortable - if not, how frequently does easy_to_borrow change and will it introduce significant survivorship bias if I assume only equities that are shortable now where shortable e.g. 5 years ago.

Thank you for any help.

@yoshi, this would be a great feature to have as i am facing a similar problem at the moment. At least, it would be great to know when the ETB list gets updated.