A substitution of trustee is completely different. All that states is that the lender wishes to use a different company to handle the trustee sale in the event the foreclosure should happen. It is a notice of public record that informs you that a party to the original trust deed has been changed.
Hope I helped! When you see a Notice of Trustee Sale posted on the premises in an open and notable location then the sale date will be posted on the notice. As a tenant you will have 60 days from the time you are served with eviction papers AFTER the sale before you will be forced to vacate.
Diane Wheatley, Broker