I'm going to take a wild guess here......

unless they find land to apply it on, they will need to send it to a landfill,  and the tipping fees to landfill this stuff will not be cheap. So, that is why they may be willing to haul and spread it for free - and be further ahead.   You can hint around on Monday, and see if they divulge that info........

There was raised a good point about the timing of when field applications occur.  That is a legitimate concern.

You say this is coming from a packing plant.  Does this stuff have an odor?  does it have to be mechanically incorporated?  If so, how soon?

I am wondering if there is a possibility of composting this stuff during times when field application is not a good idea. 

Are you a corn and soybean grower?  what is the possibility of harvesting corn stalks, and using them to compost this stuff - at least during a portion of the year.  You would give up the free spreading for this. They could haul and dump, and then it is "your baby". However, if you compost it before spreading, you would have a more stable product, and you would have your fields all torn up by spreading when it is not fit.

Just thinking out loud here..........  just something to consider......