You could argue (poorly) that the runners should be dq'ed, as both the runners and the vaulters had priority on that strip of track, and the runners initiated contact.
How does meet management avoid an issue like this? The PV runway intentionally blends into the track, so that they can use the extended length. Once the prior person vaults, you have 2 minutes to jump. So, if all the vaulters use long run-ups, then there is pretty much always going to be someone standing on the track getting ready to jump. Some people might like to stand at their tape for a minute before going, in order to get in the right headspace. If that is part of the pole vault runway and they are on the clock, how are you going to tell them to move just because the starting official blew the gun even though the prior event was not finished.