The twitter post/feed that the OP referred to has since been deleted by the original poster
I have sent a PM to discuss requirements.
For more information the tests were both done using USIM (UICC), one from the O2 network and one from Tesco. The O2 phone was a Galaxy SII and the Tesco phone was an iPhone 4s.
I saw this story the other day explaining the outage a bit more
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I would imagine you could connect for a short time due to issues mentioned here with user authentication, but this seems to be fixed now with o2.
For those that don't know, sim clones are designed to fail authentication with the network by sending an incorrect challenge response. I would imagine in this case (as has happened in the past when clone cards have connected), the authentication process was not done on each connection to reduce stress on the network.
I believe in past cases, some networks would authenticate on the 10th (or maybe 20th?) connection, and assume you were fine to connect in between that, allowing clone cards to connect until challenged.