A just and reasonable rate shall assure the utility the recovery of not less than all the additional costs of procuring and maintaining pole attachments, nor more than the actual capital and operating expenses, including just compensation, of the utility attributable to that portion of the pole, duct, or conduit used for the pole attachment, including a share of the required support and clearance space, in proportion to the space used for the pole attachment, as compared to all other uses made of the subject facilities, and uses which remain available to the owner or owners of the subject facilities.