No, they don't restore it all. Description says "restore a considerable amount of MP..."

So we have to wait and see. Probably it won't be that much, considering that Hi Elixir do this:

Restores up to 24% of HP (1120 max)
Restores up to 20% of MP (690 max)

I guess they will be around double that amount. But we'll have to wait and see.