The tickets will function in a similar fashion to Nintendo Wii Point cards and Xbox Live MS Point vouchers, with the exception that they'll be grouped in a non-bogus currency. Available in units of ¥1,000, ¥3,000, ¥5,000 and ¥10,000, the cards will contain a 12-digit code recognized by the PSN as a command to fill up your virtual wallet with the corresponding amount.
As for the possibility of PSN Tickets becoming available elsewhere, Sony offers, "We have no announcement regarding any changes to the electronic payment options on the PlayStation Store in North America at this time."