Proxying a request from MSPL to UCMA when the call is destined for a federated user?

Question

I'm trying to create an MSPL application that intercepts calls and proxies them to a UCMA application. An extremely simplified version of this would be something like:
if(sipRequest)
ProxyRequest("sip:[email protected];gruu;opaque=srvr:interceptor:G358JzT9SV6-uVxE3biQsgAA");
I installed my script on my front ends, and it works for user->user calls, inbound and outbound mediation server calls, and inbound federated calls, but for some reason I can't get redirection like this working for outbound federated calls. 
If I try to INVITE a user on a federated domain, the request doesn't get picked up by my script.  It appears that it's bypassing the front end and going straight to the edge.  If I install the same script on the edge, the script attempts to proxy
the request, but it comes back with a 404, probably because the edge is trying to redirect to an internal endpoint.  I suppose I have two questions here:
1-why is the original INVITE on the call to the federated user (which should be going through the FE, right?) not triggering my script?  I've set allowRegistrationBeforeUserServices to true, and installed with priority 1, which is above most other applications
on the server. 
 2-is there a way to change the edge server script to get the proxy to go back internally?  I did test creating a 302 and setting the contact header to the SIP URI of my application, and that worked, but it meant losing the original TO address
that I need inside the UCMA app.  There may still be a way to pass it through, but I don't want to start fighting with headers that may get stripped out. 
Thanks,
Chris

Answer 1

It looks like "domainSupported" is not quite properly documented.  It really does the opposite of what we document.
Setting it to true will cause only messages for domains that are locally supported to be sent to your application.  Setting it to false will allow all domains to be sent to your application.
Make sure you have it set to false (or exclude it completely since it defaults to false, another error in the docs).
When I do this my application sees the invite destined to a federated partner.  It doesn't even need to be registered before user services in this case.