Here's what I'm using for towers which I've been meaning to post and contribute to mkgmap:.
man_made=tower | man_made=mast | man_made=communications_tower | (landmark=chimney & communication:mobile_phone=yes) | (landmark=chimney & communication:microwave=yes) [0x6411 resolution 24]
This rule includes updates for rules about communication towers. In my opinion man_made=mast fits in this rule because items with this tag should be a full tower as opposed to a GSM antenna attached to a building.
This is easily removed if map makers don't want it.
Ben