We have a PIX 515 running OS 8.x. It is acting as a EzVPN server and multiple PIX 501 devices connect to it which works fine. The issue that the locations with the PIX 501 devices cannot communicate with one another (over the VPN via the EzVPN server). They can all connect to the main site though.
The head site does have the "same-security permit intra interface" command.