This is turning out to be more of an investigation! To come to any conclusion, we still need more details(for ex: the charge the wire was carrying,etc
Anyway, now, if your shoes are not charged and you put your shoe on a electric wire, there are just some possible reasons as to why there was a shock:
1) Your shoes had acquired a charge, on contact with the wire, which could mean there might have alredy been some moisture(sweat). Even moist air could make your shoes moist. Water(moisture) molecules would have been absorbed by rubber. And as a result the sole would have conducted electricity, creating an electric shock.
[2)(On a lighter note...) Your shoe may have had a hole!:)]
regards,
math_way