We had a really interesting presentation on non-revenue equipment last month at the local club (
www.ovar.ca). Virtually all CN's cranes of this type were built in the early 1900s as steam powered cranes. We did not see any original pictures, but it is not hard to imagine them with a tender... although some are big enough to have onboard storage of fuel and water.
By the 1950s it seems about 1/2 were converted, and 1/2 were not, so you cantake your pick. They also had a wide variety of paint jobs that were continuously changing, due to company look vs safety debates.
This is a diesel crane that was built as such:
http://www.rr-fallenflags.org/cn/cn50372agh.jpg
Nowadays they mostly use hyrail-type cranes, although the lifting power is not quite the same:
http://www.railpictures.net/viewphoto.php?id=84708
If this is the crane you are taking about, it was built as a steam powered machine, but has a 50% chance of being converted to diesel by the late 50s:
http://www.townshiptoytrains.com/HO scale/ho rolling stock/140-7525.gif
Chances are that if it is enclosed like that, iand has a very short, or flush "stack" it has been converted. In the steam version, they tended to be more open at the front around all the winding gear, and have a slightly taller stack, but that is only a generalization.
Andrew