I’m not sure if there are any stipulations on this or not. My
guess is that they should not be. But I would certainly prefer that to them all standing up there like concelebrants
before the priest receives.
Back in the days before more guidance was given, the pastor at the parish I grew up in used to have all the EMHC’s come up into the sanctuary during the sign of peace and he would actually distribute Communion to us during the
Agnus Dei so that we could all partake once he did (he did this only to save time, not because of any wacky theological agenda). Of course, as it is so ingrained in me to immediately consume the host, my first time as EMHC, I consumed right then and there during the
Agnus Dei before the priest did!

Thankfully, once some statements came out with more specifics, he stopped that practice.
I like the way my present parish does it. The EMHC’s sit wherever they normally sit (they don’t process in or anything). Once the priest has received, they come forward but do not enter the sanctuary. The priest distributes Communion to all of them and then hands them each a ciborium or chalice and they go to their places.