The answer is that – at this time – this is not something WooCommerce Tickets facilitates out of the box. An ability to pool inventory in this way is definitely something we realize a number of users would like and adding your own voice in support of this over on our feature request page at UserVoice is a great way to go here.
In the short term, I’m afraid, it’s something you’d need to implement by means of a customization (if this is an essential requirement of your project).