Yes. Lightning can expolsively ignite the moisture within the heartwood and blow-open a non-detectable linear crack but if enough life is present up top many times these cracks repair, but don't take my word for it. Caution caution caution.
Another thing entered my mind - although I'm opposed to the "eradication and control" efforts of the State of Fla. for citrus blight and canker, as long as science behaves the way they do for epidemic avoidance (yeah right, like removals are working effectively), I would cash-in on the programs. Get out there and work the extension offices, city parks depts, and reality groups, etc. Offer reduced rates for area-wide removals. Neighborhood groups, talk with them or organize meetings - lower rates (I know you can do this) and get busy. These people are shocked, upset and depressed they're losing some valuable trees so walk gently and offer group discounts.