And I can confirm it's a sequence of characters that means it's obviously encrypted data - and totally useless to anyone that can't decode it and turn it into something useful.
Correct. From what I can glean from publicly available documents, the internal ATOC standard for the barcode is RSPS3001. It seems this standard sets out the general requirements for barcoding and the security layers it uses - and it seems it's using public/private key encryption, much like HTTPS does.
From what I gather, each TOC will have a
private key with which it will generate and cryptographically
sign unique barcodes for the tickets it sells, even for journeys not made on its services. Doing this will show that a TOC did genuinely create the ticket, and which one. The scanners will contain copies of all TOCs'
public keys to decrypt the barcodes, so there's no 'online' requirement for establishing trust with the ticket.
If ATOC decide to do it properly the scanners should go online regularly to check for revocation information, so even if a TOC's private key (for encrypting the data) ends up in the wrong hands, the devices will be able to automatically reject any tickets signed with the bad key. How that would work with Advance tickets signed with an old key, printed before the key was changed, would be a challenge, but I hope they don't choose to overlook this important requirement of ensuring trust. If they don't, it would mean once a TOC's private key is leaked (or hacked), they would have no real method of stopping the holder of that key creating tickets that the system would inherently trust.
The barcode doesn't seem to store a massive amount of data, it's unlikely to be more than what's on the magstrip. At a guess (without knowing what's on the magstrip!) I'd say start/end points, ticket type, validity date(s), a serial number and a checksum.
EDIT: Sources:
[1] Marketing slideshow from Masabi, the company contracted by ATOC to work on its barcoding technology
http://www.slideshare.net/masabi/selfservice-eticketing-on-selfprint-and-mobile-given-at-travel2020 (slides 18-19)
[2] List of ATOC standards, found via Google
http://www.atoc.org/clientfiles/fil...Standards Web Pages Index 20120207 v02-00.pdf (page 2)
[3] I am an IT Systems Administrator and it's my job to understand how complex systems like this work