I'll second what Storebror stated. Our little coop group uses HSFX exclusively for online with Triggers, however, certain Triggers definitely don't work online. From what we've been able to determine (only some experimenting), generally speaking, if the Trigger involves a 'stationary' object (i.e. a light appearing, or smoke appearing) it won't work online. The same "Apparition" trigger with a moving aircraft or moving vehicle spawning however worked OK online (i.e. a flight shows up or a vehicle column shows up at the appropriate spot etc). We've also used the "reporting" Trigger online with no issue (i.e. an enemy aircraft enters a Trigger area and all players see the message). Prior to switching to the Command and Control mod by Checkyersix we were using that type of Trigger online to simulate air search radars to decent effect.
I have the latest and greatest BAT but have not tried mixing C&C objects with Trigger objects as yet but expect that some of the online issues may still be there. I know that the C&C objects such as the SAR object which would crash in HSFX works flawlessly in BAT...again only offline.