& +Werner Nieke
look back through some of my other comments on this post. I've been trying to simplify it. If you don't understand, ask.
I am not missing a "Start a Hangout" button when I log in as the page, but consider this:
You can not start a Hangout On Air with the new username and password you set for the page.
Pages still cannot be linked to Youtube accounts.
After setting up your login credentials for the page, and Gmail account if you wish, you will still be starting Hangouts On Air while logged into your personal account.
While logged into your personal account, go to your page (acting as the page) and start the Hangout.
In other words, it works just like it always did, but now you can use Apps in the Hangout.
The Youtube stream for the HOA with be broadcast on the channel linked to your personal account, but the Google+ post will be shared from the page. Again, same as always.
The login credentials you create do not make a full Google account with full permissions.