Not likely. Maybe in the parking lot, but not near the field. Poison ivy is not lush green but rather yellow/green. It has three leaves and a red stem. It would grow as a weed creeing on the ground, not covering walls (though it can climb, usually on trees). Not everyone is allergic to it. If you do catch a case of it, mild hydrocortizone cream usually helps. If it gets miderately bad, try a Benedryl pill for a couple of days.
No, the 'ivy' at Wrigley field is not of the poisonous kind. It was planted back in 1937 by a man by the name of Bill Veeck. For more information on the Wrigley field, check out http://en.wikipedia.org/wiki/Wrigley_Field.