[DOUBLE POST, sorry]
Well, I didn't figured out how to access the data from the iFrame... But I did a workaround without using the iFrame Object.
For anyone interested (sorry if I get any terms wrongly, I use Construct in portuguese):
-----
-Using AJAX, BinaryData and Video game objects.
-On Start of Layout, set AJAX binary response to BinaryData Game Object.
-Still on Start of Layout, request via AJAX the URL "https://link.com/video.mp4" with the tag "videotest" or anything else.
-AJAX On "videotest" completed, set Video source (H.264) to BinaryData.GetURL. Don't know if it works using WebM or Ogg Theora, but it probably does)
-----
This will make the video play after the time it takes to download (you can see if it's downloading using the Video On Progress event).
Doing this way I can use On Video Ended to trigger the action to change the Layout.
See y'all!