Does a foreclosure of a mortgage or lien under a deed of trust extinguish a leasehold interest?

Both real party and amicus have questioned whether the City and County of San Francisco has the power to enact ordinances which are contrary to established contract and real property principles. They maintain that foreclosure of a mortgage or lien under a deed of trust extinguishes a leasehold interest and no landlord-tenant relationship exists between the purchaser at a foreclosure sale and the tenant of the mortgagor or trustor. Real party and amicus cite McDermott v. Burke (1860) 16 Cal. 580, 589, in which the court stated "that the legal rights of the lessee were extinguished by the proceedings in the foreclosure suit and sale following the decree thereon. ... There is no privity of contract or of estate between the purchaser upon the decree of sale and the tenant. The purchaser may, therefore, treat the tenant as an occupant without right, and maintain ejectment for the premises.... The relation between the purchaser and tenant is that of owner and trespasser, until some agreement, express or implied, is made between them with reference to the occupation."