That looks like an amazing railfan weekend! I guessed correctly that jiggers are what we call speeders (track inspection car) in the US. You don’t see them in use much anymore because even the smallest Class 3 shortline will usually have a Hirail truck equipped with retractable bogies.
And I can’t imagine even an employee being allowed to borrow a truck or piece of equipment from a major railroad in the US.
And I can’t imagine even an employee being allowed to borrow a truck or piece of equipment from a major railroad in the US.