An interval timer is not going to rollover on the calendar date.
The only way that embedded controllers might "fail" is if their
watchdog data collector / management system fails its own uptime
calculations and forces a reset of all components at once. But,
that isn't how NMS systems work, so there really isn't anything to
worry about except for the lunatic fringe. Besides, even if the
controller fails, it will fail-safe -- these things fail on a regular
basis and the system wouldn't work more than a day if they failed
in a bad way.
In my past lives I've developed network management systems and
emergency management systems (police/fire/ems dispatch). None of
those will fail due to Y2K -- not ours, and not our competitors'.
There just isn't any failure condition that depends on the calendar year.
Reports might get messed-up, and payroll might get screwed, but
control systems are built with the assumption that the calendar date
is only for human consumption.