Here the announcement only succeeds if the pagat wins the last trick itself. If an opponent captures it on the last trick the announcement is lost — but the opposing side gains nothing in particular for it.
I keep hearing, though, that elsewhere the bonus (or even double) goes in that case to whoever captured the pagat.
How does it work under your rules: does the opponent get anything for capturing the pagat on the last trick? And may the opposing side announce pagat ultimo too, not only the declarer?