I reached out to NXP Semiconductors, a provider of NFC technologies, to answer your first question. NXP informs me that it is possible to develop a SIM [subscriber identity module] card with NFC capabilities. Gemalto offers a SIM card with NFC capabilities, known as DIF SIM, while Bladox, in the Czech Republic, also provides such a SIM card.
As far as Vix ERG goes, NXP notes that that company is just the system’s installer, and not the manufacturer of the Octopus card, which is actually based on Sony‘s Felica transponder, utilizing the secure ISO 14443 air-interface protocol. All contactless fare-collection systems are RFID-based, and most are built on the fundamentals of the ISO 14443 protocol (though some utilize the ISO 15693 standard). Vix ERG has performed installations using NXP’s Mifare transponders.
Yes, there are NFC stickers that you can place on a phone or some other object in order to turn it into an NFC-enabled device. The following articles discuss these stickers, and explain how they are used:
—Mark Roberti, Founder and Editor, RFID Journal