The AI dispatcher(s) don't do a great job when it comes to ensuring that the highest priority trains get to their destination on time. I was stopped behind slower services at least five times and even sent to the opposite track for no apparent reason - leading to a 25-minute delay. This is a regular occurrence. I have done 5 full return trips between Warszawa and Katowice since I bought the game by the end of April but I was not able to arrive on time ever, due to the poor AI dispatching. Often my train and a slower service are sitting at the same station and then the slower, lower priority service is sent out first so I can only follow them leading to constant slowing down. Often, on the "high speed" ETCS section I end up crawling at speeds of 40-80 km/h due to spacing until eventually, the AI lets me overtake the slower service.
This aspect is very unrealistic. I haven't been on any Polish train yet but have travelled on numerous highspeed trains and the common goal is to ensure these trains can travel uninterrupted at track speed without having to slow down for slow service ahead of them, let alone, crawl behind them or released only after they are released.
I am optimistic that this will be looked into so it will be possible to follow the timetable consistently, not only "sometimes" when the stars align. It all comes down to how the AI dispatcher prioritizes the services, and whether it recognizes early on a potential conflict that can lead to the higher priority train having to slow down.