That is where the the few leftovers from the 5th Division starts the campaign on their way to Germany (I think is their current plan). It is the same on the Swedish map, the leftovers from the 2nd Marine Regiment starts in Töreboda and plan to move to southwest (to Alingsås) where they think they can re-group. The players don't start there, they don't don't know about this, they know what they planned to do after the failed operations (last page of the intel), but not where they are (or any true locations).
But the Referee's Manual specifically states in several places that the characters begin the game near Kalisz after Soviet forces overwhelm the 5th Division.
"In Poland, the US 5th Infantry Division is pushed back and then crushed at Kalisz, the survivors fleeing into the woods." (page 9)
"What might be the final large engagement of the war took place near Kalisz, from which the characters emerge on their own." (page 11)
"The default way to start a campaign of TWILIGHT: 2000 in Poland is in the immediate aftermath of the final battle of Operation Reset close to the Polish town Kalisz, with the PCs as part of the US 5th Mechanized Infantry Division, now scattered and running for their lives." (page 31)
Since the timeline mentions 5th Division getting pushed back to Kalisz but doesn't mention from where, I'm guessing it's Złoczew since the map (which is outdated at the start of the game, I think) shows the 5th there.
As a side note, I think I found a contradiction in the game's fiction. The timeline says that Operation Reset began in early April 2000 and after about a week of NATO gains, it all went to hell, ending with the 5th getting crushed in Kalisz (page 9). But page 11 mentions Soviet forces broke the 5th Division in early July. So I ended up following the timeline and used April 14 as the start date for a campaign. We had our first game a few days ago, using Foundry. No combat yet, just shaking out the travel rules. It's been raining for 2 days straight and one of the characters now has hypothermia. One the players wrote to me: "Definitely curious to see how other parts of the system work (combat, vehicles, setting up bases) - but at this point I like our odds of just dying of exposure before any of that becomes relevant."