Ignore monitor hotplug events in idle detection?

[Will Rouesnel]

Running with a triple-monitor setup on a radeon card, with the
open-source driver my PC will never blank the display. Once the displays
switch off, the third monitor (connected via display port) issues a
hotplug event for the monitor which causes the display to wake up as
though the computer is no longer idle.

Since this ultimately originates from xorg's IDLETIME detection, is
there some way to tell xorg to ignore the hotplug events originating
from monitor's being connected/disconnected as part of the IDLETIME
calculation ?