It's hard to say if she's given up on the King St. site or just exploring. A Peregrine Falcon was first spotted at Downsview this winter on December 13. If that was indeed the first sighting of Ivy (and I have no reason to believe it's not because we rarely see Peregrines at Downsview...it was my first time since 2013), that means that she's made trips between King St. Nest Site and Downsview several times.
So yeah it does look like she's exploring all her options.
On a side note while at Downsview on Jan 3, she was harassing quite a number of Red-tailed Hawks. This is a park known for its RTH population, even in winter.
This is a short video I shot of her doing this but the sound is terrible due to strong wind buffeting so turn down your speakers before clicking on the link:
http://www.youtube.com/watch?v=tx1Xsv1zMUQ