Ticonderoga Securities’ Brian White, fresh from an October trip to China, writes that the buzz surrounding the iPhone 4 and iPad there is stronger than ever.

“Clearly,” he writes, “China is catching ‘Apple fever.'”

He cites conversations with China Unicom (CHU), Apple’s (AAPL) exclusive partner and the second largest carrier (162 million subscribers) in the world’s largest mobile phone market, in which he was told that “the opportunity for high-end smartphones in China is over 100 million units.”

Even more intriguing, he quotes a report in Thursday’s Chengdu Chinese Commercial News that mentions a newly signed “cooperation agreement” between Apple and China Mobile (CHL) — the global giant of mobile phone carriers with roughly 815 million mobile subscribers.

The nature of this agreement is unclear, but White recalls earlier reports that ten China Mobile stores in the Beijing area were offering a SIM card-cutting service that trims SIMs to fit the iPhone 4’s miniature slot. There is also an iPhone 4 microSIM card highlighted on the China Mobile website, he notes, and according to Thursday’s Commercial News report, production has started on a “small card” that might fit the iPhone and the iPad.

[Follow Philip Elmer-DeWitt on Twitter @philiped]