https://www.epo.org/en/service-support/faq/applying-patent/patent-prosecution-highway-pph/pph-and-other-acceleration-0

What is the difference between the PPH programme and the PACE programme?

The main difference between the two schemes pertains to the utilisation of available work results. Under PACE the European application is “taken out of turn” for search and/or examination, while under PPH the application is processed out of turn and the examiner is explicitly asked to take into consideration available work results.

However, PPH-based utilisation at the EPO follows the so-called discretionary approach, which means that the EPO examiner will him-/herself define the extent of reliance on the OEE work results.