Again, what is the difference between this and clicking a link? Instead of showing a link , they show a button is it? Adding a bunch of crap into email body is worth that?
This is right out of Microsoft's embrace/extend playbook.
1. I book a flight, and get a flight confirmation email from the airline. It includes a machine-readable version of my flight info in the metadata.
2. I press a button, and the flight gets added to Google Calendar, or a flight-status tracking app, or a shared travel calendar service for people who fly a lot. Note that this stuff doesn't need to be written by Google; it's an open format.
This is right out of Microsoft's embrace/extend playbook.