After setting up Exchange 2007 Edge and Hub, you can verify their configuration via get-TransportServer.

On Edge and Hub, two anti-spam settings are important.  You can use "get-TransportServer | fl name, anti*" to show the status of anti-spam related properties.

Assuming that you have 1 Edge and 1 Hub with antispam enabled only on Edge, you will see the following results.

On Edge machine
Name                   : EdgeMachine
AntispamAgentsEnabled  : True
AntispamUpdatesEnabled : True

On Hub machine
Name                   : EdgeMachine
AntispamAgentsEnabled  : False
AntispamUpdatesEnabled : False
Name                   : HubMachine
AntispamAgentsEnabled  : False
AntispamUpdatesEnabled : False

When get-TransportServer is issued on Edge, antispam status is reported correctly.

When get-TransportServer is issued on Hub, both Edge and Hub status are reported.  However, antispam status of Edge is reported incorrectly.

This takes place because it is represented as a boolean value.  It can either be true or false.  "Unknown" is a better value.