For PCT applications entering the European phase where the EPO also acted as (S)ISA, accelerated examination can, in principle, be requested at any time, for example
When accelerated examination is requested, the EPO makes every effort to issue the next office action within three months of receipt by the examining division of the application, the applicant's response under Rule 70a or the end of the period under Rule 161(1), or the request for accelerated examination (whichever is later).
In particular for PCT applications entering the European phase where the EPO acted as (S)ISA, accelerated examination can only start after expiry of the six-month period under Rule 161(1), even if acceleration has been requested under the PACE programme. In order for examination to start immediately, on entry into the European phase the applicant must explicitly waive the right to the communication pursuant to Rule 161(1) and Rule 162(2) and fulfil all corresponding requirements (see the Notice from the EPO dated 30 November 2015, OJ EPO 2015, A94).
The EPO strives to produce subsequent examination communications within three months of receipt of the applicant's reply, provided that the application is still being processed under the PACE programme (see E‑VIII, 4).