I presume you have looked into quarantine regulations regarding rabies and other diseases?
I don't know all the regulations but I think you would need to check first, especially if you are on a flight that isn't non-stop and is in transit in another country. Different countries will have different regulations. I would imagine most will want up to date vaccination records for your dog.
As regards costs and conditions, I think you would need to check with the airline you will be flying with. Different airlines will probably have different regulations regarding carriage of pets.
Check with the Polish Consulate or Embassy to find out what the rules and regulations are for the entry and exit of pets. 2nd: check the with airline about their policy of handling and transporting pets. 3rd: is the flight direct from YYZ to WAW or will it be making stops in between and how long the stops are, if any. If there is any stops enroute, how long are the stops for and will the dog be given a chance for a washroom break? Also, does the dog require any medication to be given at specific times of the day? If so, check with the vet as to what kind of papers you will need to carry with you on behalf of the pet and what kind of meds that are being given to the pet and instructions for giving the meds, if any. Also, check with Canadian Border Services about the rules for re-entry with the pet. If the dog requires meds, is it advisable to take the pet with you, considering the amount of stress it will get in regards to the flight.