On a website: How best to `list` multiple venues (about 50) that are not owned but tickets are sold for (and not the only website that sells tickets for that venue) - I assume Google My Business is out of the question - how about schema markup? Any other suggestions?
Jason Duke: The other alternative is the one you inferred would be a "no go" - GMB verification.
If you`re legitimatly selling tickets to these venues then I can`t see much of a problem asking the theatre owners to give you a call when a postcard arrives, especially when you explain to them it is to prove you have the rights to market services performed at that address.
The worst they can say is no, and if they do you`re no worse off than you are right now.... Hence there is only an upside by asking :)
Stockbridge Truslow: There may be a better way to do this, but here`s one way off the top of my head.
You are a seller (http://schema.org/seller) of tickets for an organization (http://schema.org/Organization) which has a certain event and performer (see the organization listing). You might also make use of the buyAction and several more on there too. The trick is in organizing it all on the site - looking by venue, date, etc - they`ll all be arranged a bit differently.
This won`t get you a google local listing, per se, but you should get some referrals from concert tickets near me type searches.
Stockbridge Truslow: You might start from the event side of things too... that Organization can have events (http://schema.org/Event) and, technically, that event (or the tickets to it) are yours to sell. So your tickets become a part of the "offers" in the event.And then, of course, the venue is the "location" of the event.