BMW clearly is aware of the issue NOW as sulev tanks after the E46 were indeed serviceable. My point is that they obviously had to have felt the pain warranting all the tanks for the E46 platform so you would think designing a non-serviceable tank of any sort would be a thing of the past, clearly not the case.

As for the CA emissions warranty, my understanding is that it has nothing to do with the cost of the parts but rather their relation to reducing emissions. For instance the M56 valve cover, radiator, oxygen sensors, converters, etc were all covered under the 15yr/150k emissions warranty for the E46 sulev regardless of their cost. Also, the warranty was tied to the car, so no matter how many owners the car previously had emissions related parts were covered.