Since WM knows about JBI, and since JBI's margins appear to be much much higher than Agilyx's, I'd be willing to bet that if JBI were able (scale/operationally) and willing (duh!) to do business with WM, they could.
They'd merely have to offer more than the 20% they offer to RockTenn, to be more attractive to WM than Agilyx is (since long-term, a company who controls a plastic stream is better off with Agilyx's poor margins but high % of revenue).
But for now I'd rather see them execute with RKT, and not bite of more than they can chew. Other deals will follow in-time, and JBI has a comfortable position with (apparently) the best margins in the business. If/when a shakeout occurs in the WtE sector, Plastic2Oil will undoubtedly be among those left standing.