I think it's generally not the case, but I am actually surrounded by shopping centres with both. I live five minutes away from a shopping centre that has a Big W and a Kmart (and Safeway and Coles) as the only major stores in it. I live twenty minutes away from two other shopping centres with both a Big W and a Kmart (and a Target).
But I can't get to any of them to toy shop until the weekend :(