The short answer is most likely open. I've only been down there in winter once on a Search and Rescue mission about 8 years ago. It's very rugged country, the stream sides are treacherously icy and lots of big cats too.
I have to ask, why you want to go to such an inhospitable place to fish? Yes, it's beautiful but I wouldn't think the fishing would be good enough to make up for the royal pain in the butt it's gonna be trying to lay line to the fishes.
If you go PLEASE give a full report when you get back. And remember to tell someone where you are going and when you expect to get back. It makes it more likely SAR will find you alive if something goes wrong.
The 7.5 TOPO is Big Bull Mountain Quad.
Here's a link to some pics a guy took of the area in winter. He went in from the Canon City side.
And here's his post about the area.