This is the response we just got from Development on this question:

2) When the TSM Server is performing various processes, there is a priority
for the mount point requests as to what will take precedence. The Tivoli
Storage Manager for AIX Administrator 's Guide lists the preemption order
that the TSM server would follow in Chapter 16: Managing Server Operations -
Mount Point Preemption. Please note that if the NOPREEMEPT parameter is used
for the TSM Server, this will override the normal preemption processing.

Paul D. Seay, Jr.
Technical Specialist
Naptheon, INC
757-688-8180