AFAIK, it isn't again Fox rules to put something in downstream. You just can't disconnect the output between the IRD and the splicer and connect it to a splitter to get at the HD.
That said, I hadn't looked the the engineering we page in ages. Here is what it has to say:
FOX SPLICER MANUAL V3 ADDENDUM
This addendum covers additional features in the upcoming "V3" release of code. To enable these features, please contact FOX Splicer Support to arrange for an upgrade.
Included is information on Local Logo Loading, Emergency Text Crawl Alerts, Audio Breakaway, and Enhanced Video Monitoring. The addendum is located HERE or at the Splicer Manual link above.
ALERT GRAPHICS ARE HERE!
FOX continues testing the FOX Splicer Alerting API with the support of EAS ENDEC and Weather Alerting manufacturers. Digital Alert Systems has successfully tested their DASDEC with the FOX Splicer System including text crawls and EAS audio breakaway. Trilithic has successfully initiated a test text crawl on the FOX Splicer System during remote testing. Sage Alerting Systems has announced that an upgrade is now available for the Sage Digital ENDEC Model 3644 to use with the FOX Splicer network API for alert crawls.
So, sounds like it is definitely here.