Someone has already looked into this...
http://www.stormingmedia.us/54/5459/A545953.html
Tomahawk data
http://www.worldhistory.com/wiki/T/Tomahawk-missile.htm
another site quotes
"because of the similarities between SSGNs and SSBNs, friends and foes will be unable to tell initially whether a missile launch involves a conventional Tomahawk cruise missile or a nuclear-armed Trident."
I imagine one disincentive for Tomahawk-N is that it's even harder to determine whether an inbound Tomahawk is nuclear or not, thus creating the possibility of mistaken retaliation.
http://www.thebulletin.org/issues/nu...3nukenote.html