If you can prove that your occupancy falls within the scope of CCP 1161b, then because that code section provides an exception to CCP 1161a, then you would be entitled to a 90-day written notice of termination of tenancy -- or to "ride out" a fixed-term lease.
Plaintiff's interrogatory response that "this is not a landlord-tenant eviction," seems to me, non responsive, and potentially subject to being used in a summary judgment motion to prove that there is no evidence to support plaintiff's case (depends on the precise questions by defendant -- which I cannot consider, because it amounts to practicing law, and that's not permitted in this forum).
However, The burden of proving that the CCP 1161b exception applies is defendant's, because only defendant is likely to have the documentary proof that he or she is either under a month-to-month lease or fixed-term tenancy with the property's former owner.
I don't see that defendant's interrogatory response operates as an express admission that would vitiate CCP 1161a, because CCP 1161a does not require a landlord-tenant relationship. To the contrary, the exception of CCP 1161b is what requires the landlord-tenant relationship.
So, while I understand your point, I don't think that it's as straightforward as you suggest.
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