Board Thread:Questions and Answers/@comment-2.98.50.212-20160427082522/@comment-71.83.236.251-20160428034713

Probably no on the choice. It's probable that Holy Grail War takes advantage of the natural function of a Heroic Spirit to have copies. These copies are normally ego-less, and it is a unique function of the Third Magic to grant egos to Servants. Since the World seems to normally summon ego-less Heroic Spirits, it's likely the Heroic Spirit has no say over being split and the Servant has no say either. It's notable that the Alaya cannot summon a true Heroic Spirit to be a Counter Guardian.

Servants are seemingly somewhat conscious in the Throne of Heroes. This is because the Servants send back memories to the Heroic Spirit in the Throne of Heroes. This is a unique phenomenon that occurs because Servants have egos and thus memories. The Heroic Spirit can read the memories of a Servant like a book.

The Throne of Heroes also seems to automatically supply and cull the knowledge of a Heroic Spirit based on the World. Servants would have knowledge of other Heroic Spirits due to the Throne of Heroes, not the Holy Grail. The Throne of Heroes is also said to cull Gilgamesh's abundant knowledge due to his over-bearing Clairvoyance that peaks at alternate worlds by culling it down to the world Gilgamesh will be summoned in.

I would recommend going to the 'Servant' page and reading the very first reference at the bottom directly yourself. It talks about Heroic Spirits and Servants.