As for the timing of the court's ruling, some Egyptians may see a conspiracy behind it in which the old regime seeks to reassert power following Morsy's ouster, Trager said.
"Others, who see this as a normal, understandable process in which a leader who they now associate with a better time in Egypt is now being released, will give a different response," he said.
"I expect that Egyptians will be divided on this as they have been deeply divided in every point of the last two-and-a-half years."
Tamarod, the anti-Morsy protest movement which called for the mass rallies that led to his ouster, said it was not surprised by the ruling on Mubarak's release.
In a statement on its official website, the group blamed Morsy's administration for failing to do enough to push Mubarak's trial forward.
The group called for a retrial of the former president, with new evidence before the court, and for Morsy to be put on trial as well.
The military, which has governed Egypt since forcing Morsy out of office, continues to hold him in detention and controls the judiciary.