I have no doubt you will get there. There is a replacement timetable (
Ersatzfahrplan) in place. 12 hours before your time of departure use the
real time departure engine. This should show all the planned long distance services.
What it doesn't show is the replacement buses[1] for the Berlin-Warszawa-Express or any similar ones. I think the only way to find out about those was to ask at Berlin Hbf. Nowhere else had a clue they even existed - not bahn.de, not HAFAS, not the staff at Frankfurt(Oder), not any posters anywhere, while at 05bleugh there weren't a lot of staff around at Berlin Hbf to ask.
Sometimes I moan about slightly poor information in the UK at times, but this was something else. The experience reminded me of flying during the ash cloud incident - felt like trying to hit a moving target finding an itinerary that would work as regional trains were cancelled all over the shop, often less than 12 hours before departure. And you couldn't use yesterday's example, because HAFAS doesn't keep real time information for trains that have finished their journey.
Really, really unimpressed. It was an enjoyable little explore and a fun little challenge for me as an expert public transport user, but if I'd been a normal passenger I'd have decided to drive or fly next time.
[1] HAFAS seems to turn off the display of buses by default - stupidly it doesn't distinguish between rail replacement buses and "normal" buses, so if you select "bus" you often get a load of garbage. But the BWE replacement buses were *definitely* not in. It seems the PKP site (and in Polish only) was the only place they were recorded online, even though they were DB operated "IC Bus" branded coaches.