Wow, I don't know where to start, also I don't want to be snarky, but...
First since just as many people CRH quarters but you hardly ever find a silver why wouldn't they mix in silver quarters? Get more people to order quarter boxes? I am hoping you are being sarcastic about that view.
First how do you explain two recent boxes last month that each had 18 90% and 34 and 42 40% respectively? and yesterdays Loomis that had 4 90's and 5 40's?
To the best of my knowledge the way silver gets in the stream is when people dump it in a coin machine. But that doesn't happen everyday so for the most part boxes are going to be silver-free with the occasional coin and the rare monster box. From what I have seen most couriers hate hauling coins, they prefer bills. Many banks don't even know they can order halves, they are used to dimes quarters etc.
I think Loomis, Guarda, Brinks, salting boxes with silver is on par with the Lockness Monster, big foot, 9/11 being done by the US government... It is interesting to talk about but is it real?