Archived redo missing on primary but present on standby - can this be used?

Hi,

    My customer populates his system test database by means of an RMAN Level 0 backup taken from his primary database, which he restores to the system test database, then he applies archived redo to bring the database forward to the required point in time. Unfortunately some of the archivelog backup pieces from the primary database have been inadvertently deleted. They do, however, have a physical standby database, and they have a full set of archivelog backups from this standby for the entire day. The question is - can these archivelog backups from the standby site be used to roll