Not really. Right now in the present day, the Chinese are accused of using Falun Gong political prisoners as organ harvest victims. All it requires is a corrupt system, enough political power to make dissenters think twice, and buyers who will take "a new liver now" over "an ethical liver when you reach the head of the line".

Yes, a system that's corrupt at the highest levels is another matter. But a system like that doesn't have to bother with sneaky lab switches.

I'm talking about preventing abuse at the lower levels, in a country that's still doing a good job with protection of individual rights and maintaining the rule of law. Some laws are difficult for any government to enforce; this wouldn't be one of them.