Is there a specific police force that investigates the conduct of Amtrak or other railroad employees or is it the specific railroad police force in general i.e. Amtrak Police, Union Pacific Police etc or are these forces just there to enforce laws regarding incidents concerning non-railroad employees? Because it seems like they are always portrayed as such in the media?

Are there any states that have laws that don't allow the creation of railroad police departments to operate by lowering them to the level of a private security force and/or strictly limiting the geographic area within a state that they can enforce the law? Are some by law actually multi-state police forces?

Do they still use those specially marked cabooses like the SP once did?