The employee at the Scout Store said the old pants (current style) can NOT be worn with the new uniform. He also said that ANY official uniform remains official, but parts such as shirts and pants are NOT interchangeable.
The store will let me return the pants or exchange it for something else, they just can't supply the correct size in the old style (current style?) switchbacks and the new ones are not in. Fortunately, I still have shorts and slacks that are still in great shape. I was looking forward to something a little cooler to wear.