Searched for "lead block" on
http://www.glbwiki.com/qa/search.php ...
Question: What is considered a Lead Block in GLB?
Borth: Pretty sure that's been answered before; anybody close enough to the runner and ahead of him, or who is specifically coded to "Lead Block," like the FB on many plays. 90% of the time it's the latter case that's important for skills and such.
Still doesn't answer your specific question, but it definitely narrows things down a bit from what you posted in the OP.
I also saw some references to Lead Block working for O-linemen if they are doing something specific like pulling for an outside run, but NOT working if they're just straight-ahead blocking on an inside HB run.
So, I'd say the odds of Lead Block working on Special Teams are slim, and if it does work, it would likely be only in very limited and rare circumstances... which would suggest that you can get a bigger bang for your buck with a different SA if you want good blocking on ST plays.