CECA Schedule of Equipment - Hired in Rates

Under Section B, Point 8 of the CECA Schedule of Contractors Equipment Rates, hired equipment shall be charged at invoice cost.
Whilst this is accepted for equipment hired in specifically for additional work under a compensation event, is this principle applied for equipment the contractor/subcontractor already has on site to complete their original scope of works?
I.e. the contractor/subcontractor undertakes the original works using hired equipment and then undertakes additional works under a compensation event, using the same equipment. Would they be entitled to CECA rates or invoiced rates for this additional work, as even though the equipment is hired, it has not been hired in specifically for the additional works (as it was already on site completing the original scope of works).

I presume you are on an Option A or B contract. I would suggest that if the Equipment was already on site then the rates in the publish list +/- the adjustment would the Defined Cost for assessing the effect of the compensation event