For example, any website I've built I can surely make with just a text editor but I'll lay it out with ps first. That way I can go back and check what colors / gradients / dimensions I used to speed up the process.
I would image this would require something similar but to the nth degree. That is, I count 20 something <b></b> tags to make the clouds in the mail icon. Is that really just guess and check?!
http://blog.graphicpeel.com/post/740928981/ios-icons-made-in...
... it's not the same guy, but the above blog post is the first time I remember seeing someone do iOS icons in pure CSS.
The whole thing is fun more than practical ... kind of like ASCII art for a new generation ;-)
You may be a bit behind the times: