The law in China specifies a max assisted speed of 20kph (12.4 mph),this is pretty much ignored but it does exist and Chinese governments have a way of enforcing the law when it suits them.
The problem of these e-bikes is they have too much power,800 watts is the norm,1500 watts is often.
There are over 2000 deaths per annum directly attributable to e-bikes.
There are over 120 million on the road or more accurately on the pavement because they ride everywhere from any direction and cause massive parking pavement congestion,often 4 deep.
A lot are still lead acid batteries,which may last only 6 months and when exhausted get dumped in the river.
There is no registration so when one is finished you dump it where it fails and buy a new one from Tescos China for 1900 RMB,a bit over £200.
In short they are a dangerous nuisance,occasionally you see a bicycle derived e-bike with a lithium battery,usually ridden by a middle class lady,these bikes are similar to our electric bikes,they cost about £500 so are inevitably rare,our Kudos Tempo is similar in style,these bikes seem to be more in harmony with their city usage.
The only reason the Chinese government has not clamped down on them is that it would mean wider car ownership and many Chinese cities are already at gridlock. But the Chinese will I think make ownership more expensive so as to force the population to use the new metro systems and will clamp down on the power and outlaw lead acid batteries.
KudosDave