regular contracted service providers

I think your last comment is the one that makes the decision for me: the service that these contracted employees provide is a necessity in the year-round operations of the client's facility. If they are part of the daily operations of the building, they should definitely be included as part of the transportation survey. The distinction is based on whether they are coming to the building on a regular basis to work a full-day; an example of a contracted service provider who would not be included in the survey might be a pest management provider. They visit the building on an intermittent basis and usually are not putting in a full work day on the premises.