I wonder what kind of grass they are intercropping with? Interesting because blueberries have a very shallow root system, I would think grass would choke them out.
There is a whole series on high bionutrient crop production I watched where Dan Kittredge says his blueberries grow great without any ph adjustments to his soil. He claims that if all the nutrients in your soil are perfectly balanced and stay wet at all times, you will never have to do any ph tests or adjustments.