The biggest differences are in the pre-processing of the waste. Tires are more challenging due to having to deal with the inlaid metals ("steel belted").
On a process side, plastics tend to be a more complicated feedstock, often having more "hetero-atoms" than are found in tires. So product slate may be more complicated. Tire rubber is relatively straight-forward.
Either way, the 6-12 month time-frame stated is reasonable if the plant is pre-built or most of the equipment is already on-site.