I think this tire is identical to what came on my Worksman except for the branding:
http://www.niagaracycle.com/product_...oducts_id=1384
It is a street-tread blackwall tire, and I don't think any of the local shops sell that. They all have mountain bike tires with blackwall and cruiser bike tires which are invariably whitewall. This tire is not flat-proof or anything, but seems decent enough.
My mountain bike had knobbies, and I didn't mind them. I couldn't tell they slowed me down much (keep in mind, these were cheap knobbies, not super-aggressive tires), and the hum they make is handy to let people know you're coming on the bike trail.