In Fate, can a Master summon an Extra Class Servant during a Holy Grail War, or under any circumstances? In Fate, can a Master summon an Extra Class Servant during a Holy Grail War, or under any circumstances?

For example, one Master summons Jeanne of the Ruler Class, and another Master summons Edmond Dantes of the Avenger Class. Can that happen?
If I remember correctly, in the Fate/Zero and Fate/Stay Night universes, Avenger Angra Mainyu was summoned by the Einzbern in the third Holy Grail War instead of a Berserker. This would imply that it is technically possible to summon an Extra Class Servant during a standard Holy Grail War following the Fuyuki formula.