Hi,
Thanks for the interest in our plugins again. I can help out here.
I suppose you could use the Facebook Importer to import and Facebook Event and then edit it in WordPress to export to EventBrite. I have not tried it before, but do not see why it would not work.
However, it would not sync information between the 3 installs it would essentially create 3 different places to view the event.
As for the ticketing plugins each one has similar features. You would want to choose the one that works with the eCommerce system you would like to work with.
Let me know if you have any follow up questions.
Thanks