He has already made an impression for the Grecians, scoring one and setting up another in their 4-0 win over Cambridge Utd at the weekend.
"Whether I stay is up to the two clubs," the 29-year-old told BBC Radio Devon.
"I've been here just over a week, we got a draw when we played Dagenham and a win last week against Cambridge, so I'm enjoying playing."
Wideman Scully joined the Magpies in February 2004 and made a total of 48 appearences, scoring 6 times.
The former Irish under-21 international became renowned for his erratic performances, with his inconsistency dogging him throughout his Meadow Lane career, until Thordarson made him available for transfer prior to this season.