By looking at the regulations book I would say that elk qualifies as a bull under the "any bull" definition and does not fork, so therefore it is a legal spike. Not legal in antlerless. I think the key here is "projecting above the hairline".
Definitions from booklet:
Any Bull Elk Seasons: Open only to the taking of elk with visible antlers (bull calves are illegal).
Visible Antler: A horn-like growth projecting above the hairline.
