If I understand this correctly, the "pyle" (“The People’s Bicycle Library of Greater Portland”) is the riding group "zoobombers" storage tactic that has become recognized as an art installation. On sunday evenings the bikes get unlocked and raced down the windy west hills from the zoo.
A full detailed artitcle by bike portland seems to have more info than I do. READ Wikepedia on "Zoobombers"
I found out about this too late... I did do my own zoobomb ride on my loaner fx after leaveing the japanese garden.