Location Awareness .. just can't get it working

Hello,

We have two sites, linked via a site-to-site VPN.

Each site has it's own SEPM Server, and replication between these servers is operating. Both servers are on version 12.1.4104.4130 .

I've read all the tech notes, forums posts and instructions I can find, but I can't seem to get Location Awareness to work for me.
We have client PCs that move between the two sites. I'd like clients that log in at SiteA to switch to the Group called SiteAGroup, and clients that log in at SiteB to switch to the Group called SiteBGroup.

This is how I have it set up:

- My Company
    |
    |-- Default Group
    |-- SiteAGroup
    |-- SiteBGroup

    
I have disabled inheritance being passed on from "My Company" to the last 2 groups shown above.

I have added a location called "SiteA" to SiteAGroup. I have added one entry here - to switch to this location if Gateway address matches 10.1.0.254.
I have added a location called "SiteB" to SiteBGroup. I have added one entry here - to switch to this location if Gateway address matches 10.0.0.254.

Now, say if a managed SEP client is in SiteAGroup, and it's default gateway is 10.0.0.254, it isn't switching over to SiteBGroup.

Obviously I'm either misunderstanding how it works, misconfiguring something, or I am missing some steps.

Can someone please help me with getting this working? Would be greatly appreciated.

Nev