There's a thread somewhere about this David. The short answer is yes and you don't need to line it. I think it was the Melbourne City Council which did extensive testing and found the treatments only go a few mm at most at very tiny levels. It was deemed safe.
In the last several years I cannot remember much if any conversation about CCA treated timber for gardens on this site. But you can search the site using the search function. Just be prepared for many pages of irrelevancies but you just might get some gems in the mix.
The conventional wisdom is that CCA treated timber is not used for anything to do with gardens. Based on the thought (but no one has advanced any proof as far as I know) that the toxins would or could leach.
Working on the 'better be sure than sorry' principle, I would not use it myself. My garden edges are all metal and now I've converted them to wicking beds, they are lined with builder's plastic, toxicity and leaching unknown. Frying pans and fires spring to mind!
I've read about the zinc leaching from galvanising too. My metal water tank is lined with some kind of plastic I think - it's powder-coated so perhaps whatever-that-is is in contact with the water. We don't drink the water but the food garden does.
Solution: follow your own feelings in the absence of proof.
Oh ye doubting Thomases. Here:
Please note the section about "Is it safe in my vege garden."
I'd still rather use ACQ than CCA. LOL. Just saying. However, there's no need to panic about CCA.
We'd love photos mate!