Yeah so I actually removed that extra tribe_get_ticket_form() because it’s superfluous, I’d regard it as a bug (and I’ve logged it as such – so thanks for bringing it to our attention).
The reason your code didn’t work initially was because as soon as tribe_get_ticket_form() was evaluated it was also printing out the Eventbrite form, so the second call didn’t actually do anything.
So that’s all a bit confusing and again I have logged this as a bug, hopefully it can be revised in a future version and made a little clearer. For the time being it sounds like you’re on track with this one though 🙂