I think by proxy he means in essence that everyone logging on form where he works will appear to to come from the same IP that will probabaly point to something.companyname.com - I'd have the same issue if it wasn;t for the fact pa is blocked where i work.
a number of isp do similar things e.g. AOL - as long as yourcompany is well known it wouldn;t be a problem - its not like we close everyone who uses AOL
But for your own safety if you tell the mh team, it removes any chance that a mistake is made as Assassin says.