I've put about an hours worth of research into this subject. I can truthfully say that there are PC updates that are specific for dedicated servers on RvS and AS. There is an option for dedicated server in your menu if you have the PC version but its not there under Advanced Options on the mac version. Furthermore there is a dedicated= somthing in the server.ini.. enabling this does nothing.
You would be correct ferret
When I play on PC all I see are deticated RvS servers that clans have rented out. No spectating host player, nothing. There can literally be NO people in a server. In consequence the pings can be WAY smaller on PC... but it usually isnt the case because these servers are hosting multiple games on the same comp - so actually some mac servers are faster with lower pings cause thats all their hosting! Anywho... Ubi and aspyr fucked it over on the mac community once again by disabling mac-pc support and no deticated server ability on mac(as if they need it if they cant play with PC's so I guess it makes sense)