Adam, BRC is not my area, however, I would assume that the contracted operator would be responsible for the CCP at their end and you would be receiving the units back as finished goods/repacking/warehousing only so the processing that occurs off site does NOT belong in your plan.
You would then need documentation from said 3rd party company as part of your approved supplier program. But again, BRC is not my thing. Generally speaking from a HACCP point of view this would be a "hazard not controlled by the facility" In Canada, we would use a form 9. example below
Example of Completed Form 9: Hazards not controlled by the Operator
Product name: Spices
List here any biological, chemical and physical hazards that are not controlled by the operator
Hazards
Indicate how the hazard could be addressed (cooking instructions, public education, use before date, etc.)
Untreated Spices / Treated Spices – Presence of agricultural chemicals (pesticides and herbicides) in spices above the maximum residue limits.
Farm level – Educate farmers about good agricultural practices.
Supplier level – Obtain documentation (e.g., Letter of Guarantee, Certificates of Analysis, specifications) from suppliers to demonstrate that spices were grown, harvested and handled according to good agricultural practices.
Untreated Spices / Treated Spices – Presence of heavy metals and other chemicals in spices due to water used for irrigation and fumigation on the farm and/or steam sterilization at supplier/treatment facility.
Farm level – Educate farmers about good agricultural practices.
Supplier level – Obtain documentation (e.g., Letter of Guarantee, Certificates of Analysis, specifications) from suppliers to demonstrate that spices were grown harvested and handled according to good agricultural practices.
Untreated Spices / Treated Spices – Contamination with agricultural chemicals, non-food chemicals in spices due to improper use of reusable containers at the farm level and/or supplier/treatment facility.
Farm level – Educate farmers about good agricultural practices.
Supplier level – Obtain documentation (e.g., Letter of Guarantee, Certificates of Analysis, specifications) from suppliers to demonstrate that spices were grown, harvested and handled according to good agricultural practices.