Each registered entity reports to EPA. If the parent company is the registered entity for each of its facilities, then the parent company will report. If each subsidiary facility is its own registered entity, then each of those entities must report.
If the facilities are contiguous and custody is maintained by one entity (the parent owner in this case), they may be aggregated. In that case the owner must register as an entity, and the aggregated facility must also be registered (§ 80.597(c) and (d)).
Question and Answer was originally posted at Questions and Answers on the Clean Diesel Fuel Rules (PDF)(135 pp, 888 K, EPA420-B-06-010, July 2006, About PDF)