Error bpbrm (pid=36700210) socket read failed: errno = 119 - System call timed out - file read failed (13)

If a parent job spawns 3 child jobs and you only want an operation for the parent, not the children.. use:

parent_start_notify &
parent_end_notify

And for your subsequent question, yes, bpstart & bpend can be specific to a policy and/or schedule, see this in admin guide:

To create a bpstart_notify script for a specific policy or policy and schedule combination, create script files with a .policyname or .policyname.schedulename suffix. The following are two examples of script names for a policy (production) that has a schedule (fulls):
/usr/openv/netbackup/bin/bpstart_notify.production
/usr/openv/netbackup/bin/bpstart_notify.production.fulls