The Fortran 2018 standard describes five coarray intrinsics that allow for collective communication:
CALL CO_BROADCAST() CALL CO_MAX() CALL CO_MIN() CALL CO_SUM() CALL CO_REDUCE()
They are described in section 3.19 of the summary document:
Are there plans to implement this? The release notes of the 2019beta compiler do not include this.
As far as I am aware, the collectives are not part of Intel 2019 yet (however coarray events are). See also this post: https://software.intel.com/en-us/forums/intel-visual-fortran-compiler-for-windows/topic/754283
I'm pretty sure that Intel plans to support all of F2018 eventually. Not everything will necessarily get done immediately. Progress has been very good. It at least is full F2008, which is something that can't be said for any other compiler excepting Cray.