UMich uses BlueJeans for videoconferencing.
I use the most recent version of Google Chrome and I have the "Blue Jeans" [sic] application installed. (Although the name of the service, application, and company are "BlueJeans", without a space, even they release things with the name "Blue Jeans". QA est mort!)
If I open a BlueJeans meeting URL, like this:
The external app will launch, even without the Chrome "Blue Jeans Launcher" [sic] extension installed.
However, if I open a BlueJeans for UMich meeting URL, like this:
The external app will launch, but it will do nothing for two minutes (and it's uninterruptable) before finally showing the message "There was a problem loading the application." with a "Try again" button. Clicking that button will make it work. It's annoying to wait the two minutes for the initial failure, though.
I decided I didn't want BlueJeans to automatically launch the app, so I removed its URL scheme handler from "~/Library/Preferences/com.apple.LaunchServices/com.apple.launchservices.secure.plist". That worked at first.
I wanted to make sure that after joining a meeting via the browser, I could switch to the standalone app, because the app offers better screen sharing features among other things. It did.
However, after the first external app manual launch, subsequent joinings of meetings automatically launched the app, but there wasn't any entry in the "launchservices" plist file! Mysterious!
OK, so it turns out that requesting a BlueJeans URL in a Chrome tab that has already been granted access to launch the external app may launch it again automatically. However, requesting the same meeting URL in a new tab does not.