EASEE-gas, the European Association for the Streamlining of Energy Exchange – gas, published the Common Business Practice (CBP) document 2017-001/01 on Message Transmission Protocol for Document Exchange.
This CBP, prepared by the EASEE-gas Technology Standard Working Group, was approved by the ExCom on 29 June 2017. It encourages EASEE-gas members to start using the AS4 protocol with the ENTSOG profile rather than the AS2 protocol because of security reasons and to continue using the EASEE-gas digital certificates. AS2 has been used as a communication protocol for exchanging EDIG@S documents in the EASEE-gas community since 2007 (see CBP 2007-001-02 on Message Transmission Protocol). TSOs, however, must comply with the Commission Regulation (EU) 2015/703 of 30 April 2015, establishing a Network Code on Interoperability and Data Exchange Rules, which means that TSOs and their affected counterparties active at either interconnection points or interconnection points and virtual trading points, must replace AS2 by its successor AS4.
For this reason and because the security techniques specified in AS2 are not future proof, EASEE-gas recommends to use the AS4 protocol for all document exchange in the gas market with an appropriate profile (narrowed down set of settings).
TSOs already have implemented AS4 as of May 2016, in accordance with the Network Code on Interoperability and Data Exchange Rules. EASEE-gas also recommends the implementation of the certificate exchange protocol using AS4 (ebCore Agreement Update, docs.oasis-open.org/ebcore/ebcore-au/v1.0/) by the end of 2018. The intention is to implement a central AS4 configuration management facility should when available.
Press Release: https://easee-gas.eu/download_file/DownloadFile/28/cbp-2017-001-01-message-transmission-protocol-for-document-exchange-press-release  
CBP: https://easee-gas.eu/download_file/DownloadFile/26/cbp-2017-001-01-message-transmission-protocol-for-document-exchange    
ENTSOG AS4 Profile: https://entsog.eu/publications/common-data-exchange-solutions#AS4-USAGE-PROFILE 
OASIS AS4: https://docs.oasis-open.org/ebxml-msg/ebms/v3.0/profiles/AS4-profile/v1.0/ 
OASIS ebCore Agreement Update: https://docs.oasis-open.org/ebcore/ebcore-au/v1.0/