Check out 135.265 and 135.267. This will spell out specifically what you can and cannot do. 135.265 refers to Scheduled Operations while 135.267 refers to Unscheduled Operations. I assume this operation you speak of requires two pilots or less, so 135.269 wont be in play.

Some unscheduled operators, like mine, choose to use the more stringent 135.265, however from my understanding scheduled operators are required to use this part. Unscheduled have the choice.

To answer your question about whether they can use both sets of rules, I would probably say yes. The key is to apply the standard of the regulation to what you have done in the last day, week, month, quarter, and year. If you’re legal, you’re legal. I would say in most cases going from scheduled (135.265) to unscheduled (135.267), no problems. From unscheduled to scheduled, now you’re playing with fire.

To answer your question about flight instruction, the answer is yes. The regulations say, "…no flight crewmember may accept an assignment, for ... if that crewmember's total flight time in all commercial flying will exceed..."

If I where you, I would just ask to see their operations specifications showing that they can operate under both sets of regulations. I don't see why they would not accommodate your request. But remember, the ultimate burden on whether your legal or not, rest squarely on you. The company can and will get in trouble if you fly illegal, but the buck stops at your doorstep. No amount of "the company told me this" or "they said they would fire me" will protect you from a certificate suspension.

Calling the FSDO that holds their certificate and asking the certificate's Primary Inspection Officer will be a good way for you to know for sure.

Hope this helps

johnnysnow