The Mt. Wilson Trail was open the last time I checked. I run by there in the morning, so I'll check it out tomorrow to make sure. It did close, however, not too long ago during the rains we had. There were a couple of big washouts lower on the trail. My buddy and I were hiking to the top of Jone's Peak via the Bailey Canyon Trail and then looping down the Mt. Wilson Trail. After getting to the top of Jone's and switch-backing down the opposite side back to the Mt. Wilson Trail, we noticed a lot trail work had recently been done. When we came around the last corner exiting the Mt. Wilson Trail we came upon a huge fence across the trail access saying "TRAIL CLOSED." We were like.....WHOOPS! (We had no idea since we had started over at Bailey Canyon). There were some trail workers sitting in a truck at the trail head giving us dirty looks, so we explained the situation and asked them what was going on. I guess someone was heading up the trail to decide whether to open it or not depending on the conditions. That was at least 2 or 3 weeks ago, though. So I'm almost positive the trail would be open by now.
If you're looking to summit Wilson, and for whatever reason the Mt. Wilson trail is closed, just head up out of Bailey Canyon. You'll get to a saddle eventually, then you can follow a firebreak all the way to the Mt. Wilson Toll Road just below Mt. Harvard. From there you could just follow the toll road up to the top. ( I haven't done this personally, but it looked doable).
Here's a google image of our GPS track. You can see the firebreak leading off to the toll road near the 1st trail junction.
Bailey Canyon Park is at the end of Grove Street. (Go up Michillinda, take a right on Grandview, then up Grove to the end).
Have fun,
Gusto
Edit: Ran by this morning (Wed. 1/13/10) and the Mt. Wilson Trail was open.