The job report takes it's info from the job submission and doesn't care about the accounting code.
If it comes from an unknown user and doesn't know the Job name I would assume the port is either HP Jet direct, or possibly IPP/Bonjour/Appletalk.
Reinstall the driver on one Mac but do so manually and make the port LPD and try it, it is likely going to resolve the matter, if it does, do it with the others as well.