OWS is indeed also recognized by BNQ in Canada. Canada has its own standard on industrial compostability, but it is actually a copy of ISO 17088. If you can give me a bit more information on the type of paper and type of PLA used, I can draft a test program.
For instance, do you have input on the composition of the paper? Does it contain any organic ingredients in more than 1%? If so, ISO 17088 states that these would need to be tested separately for biodegradation. For the PLA, if it is an already certified PLA, no further testing on the PLA itself will be needed.
At first sight, assuming the paper is OK and does not contain any organic additives in a concentration above 1%, the following testing would be needed:
Heavy metals, Fluorine & FT-IR: 931.0€
Quantitative disintegration + compost production: 8,035.4€
Plant toxicity: 2,743.3€
Again, this is assuming your customer is using a paper which is not yet certified and has no organic additives above 1%, and a type of PLA which is already certified. I would be happy to confirm/revise the above after having obtained some further input on the exact composition of the paper and the identification of the PLA grade used.