what kinds of optimizations are you thinking of? I don't think the engine can do stuff like defer simulating offscreen events to process them in a batch several ticks later. anything happening anywhere on the explored map could potentially affect things in the player's view. several systems (eg, trains, electricity) need to respond immediately to changes in the global state.
There are absolutely optimizations that can be made to process items that aren't visible on the screen. Everything is deterministic, cyclical and can be represented as a graph. Given the initial number of resource at a node in the graph, and a time duration, you can calculate exactly where each resource will be at any time.