Does the Miranda Rule apply when a defendant is removed from the prison population and questioned by police about unrelated crime occurring outside prison?

U.S. 499, 502, 508 [questioning of prisoner may not be custodial when prisoner removed from prison population and questioned about unrelated crime occurring outside prison].) "Because the dual elements of a police-dominated atmosphere and compulsion are absent when the defendant is unaware that he is speaking to a law enforcement officer, however, Miranda is inapplicable when the defendant does not know that the person he is talking to is an agent of the police." (People v. Davis (2005) 36 Cal.4th 510, 554.)