I set up an abuse filter on testwiki that warns the user with the MediaWiki message "snorkel-abuse" and also disallows the action. When triggering this filter using the API (action=edit) I get this:
<?xml version="1.0"?><api><edit code="snorkel-abuse" info="Hit AbuseFilter: TTO's test filter" warning="Don't create snorkel pages" result="Failure" /></api>
The only way to test for AbuseFilter being hit appears to be to check whether the "info" parameter starts with the string "Hit AbuseFilter". This seems a bit hackish.
The spam blacklist manages to do better than this, providing its own spamblacklist attribute on the <edit> element. AbuseFilter should be able to do better too.