They only have one use - to unlock EX3 Costumes in Resident Evil 6, all EX3 Costumes cost 1 Extra Ticket.
The events that give out Extra Tickets are the following:
- Pax Aeterna
- Neutralize the Threat
- Agents, Abductors, Chainsaws
All these events require a global goal to be achieved by all participating players, however the goal on the Xbox 360 is always lower than on the PS3 and the Steam goal is non-existent, so all Steam players will always get a ticket just by participating in these events.