Please state your sources
i know it is just wikipedia, but other documentations i seen, say as well that horses have been used on polish side.
http://en.wikipedia.org/wiki/Polish_cavalry#20th_century:_World_War_II
http://en.wikipedia.org/wiki/Battle_of_Krojanty
http://en.wikipedia.org/wiki/Battle_of_Tuchola_Forest
at least its interesting that the polish army even considered a use of there cavalry against the modern (in comparison to polish army) german military machine. Though, propaganda might take a big part in here, but it seems that the polish army even sometimes had a good succsess.
Though i can not find anything "serious" about, if they have been ever used against tanks, probably not really. The article on wikipedia says mainly against german infantry and even sometimes with success.
but one information is interesting.
"The same day, German war correspondents were brought to the battlefield together with two journalists from Italy. They were shown the battlefield, the corpses of Polish cavalrymen and their horses, alongside German tanks that had arrived at the field of battle after the engagement. One of the Italian correspondents sent home an article[2], in which he described the bravery and heroism of Polish soldiers, who charged German tanks with their sabres and lances. Other possible source of the myth is a quote from Heinz Guderian's memoirs, in which he clearly stated that the Pomeranian Brigade had charged on German tanks with swords and lances"
I would be interesting to read about what Guderian realy meant about the "polish cavalry" and there charge against german tanks just with sabres and lances, which sounds very strange.