I'm in Phoenix, AZ. I tossed some acorn squash seeds into my compost pile (inside an old plastic trash can with holes drilled into the sides). This was about 2 months ago. It got really cold in Phoenix, and I went for about a month without turning my compost pile. So I went out there a few weeks ago and lifted the lid. Lo and behold, I had healthy looking squash plants. So I pulled 4 of them and planted them in my container on the back patio just to see what would happen. Now it's February and look at the photo! The thing is, our growing season is from Feb to early June and then again from October to about December. So can I get squash out of these plants? I was going to take the wheels off this planter and just set it on the ground. It has a raised bottom inside so drainage is really good. What do you think?
Volunteer plants can happen quite often in composting.
You may certainly get some squash on the vines, but keep in mind that they are likely from a hybrid seed. The vegetable may not resemble the original vegetable that you had planted.
Here are some links to help you.