Here is my simple yet direct answer that I received verbally from the Head of the Traffic dept. of Shanghai (I was invited to a diner in which he was the guest of honor) (no I am not going to post his contact details). He stated that basically China like many countries have both National and provincial level laws. Much like the US and the Federal and State law. The National Law must be adhered to in China but a Provincial law my add to it or vary from it as long as it does not contradict the law. Now you might think that the Shanghai provincial law does in fact contradict the National law by banning bike from the express ways, but to the Chinese authorities, its simply an addition to what ever else is banned from Expressways. Because the National law allows bike on the expressway, I have been legally allowed (and often even have to pay at the tolls) on expressways on both 2 wheel bike and 3 wheel bike. That being said that does not mean that I have not encountered the ignorant toll booth attendant or policemen who bars my entry onto an expressway.... but TIC

In short:

National Law "yes, bikes can be driven, as long as they are capable of at least 70kmh, the operator is wearinf a helmet and there is no passenger.

Shanghai Provincial Law "No bikes. period" (which really should not be all that surprising)

Besides, every single one of us has said to someone "ITS ABOUT THE JOURNEY AND NOT THE DESTINATION" Expressways are boring as hell.... I rather be in the countryside the a large flat tarmac any day. In other parts of the world people search far and wide for country roads to ride instead of the highways and byways....