First, if a detour can be easily made (in this case it was), the main reason it is done is for equipment turns. If the equipment can't get to point B, then it can't turn to go back the way it got there. You can't run a train without equipment. Second, there is no easy way for an eastbound on the BNSF to turn and go North on the UP at Stockton. It was much quicker to keep the CZ rolling straight than it is to pull forward, then back up. However, this was done at Elvas to get from the Fresno Sub. to the Sacramento Depot on the Martinez Sub. to do station work there. It is much easier to make that move then even attempt to do it at Stockton. The only way you could have MAYBE done this is to pull down the siding into Mormon Yard, back onto the UP transfer track and head North from Charter Way, an extremely time consuming move. When a detour is set up, one the the things people in the Ops. Centers will do is calculate what detour route will cause the least amount of delay to what is usually an already late train. They will also do it to use the least amount of pilot engineers and crews required. Remember, the whole objective is to get the equipment from point A to point B as quickly as possible, while doing it at the lowest possible cost. I have never heard of the CZ being detoured over the BNSF through Franklin Canyon before, but I won't rule it out, it may have happened at one time and I never knew about it.