PWS was introduced in Rel-9 and I blogged about it here. ETWS has been around since Rel-8 and was blogged here.
In fact EU-Alert is sent as part of the Cell Broadcast Message (CBS) using new identifiers. For more details see 3GPP TS 23.401.
The following is an old video from CHORIST project, which was instrumental in providing details of working of this EU-Alert system.
Also Read: Commercial Mobile Alert System (CMAS) here.