Yes. Right-click the event, select properties, then click on Media Properties. For the Alpha channel drop-down list, select "Premultiplied". You can put these videos on the overlay track to appear on your own videos.

You'll notice that a lot of these videos will make effective transitions. Just time scene A to switch to scene B at the moment of no transparency.

Not all the included videos work. The ones encoded using the Cinepak codec won't work.