The 4 foot/5 foot rule is only mandatory on "state roads". For local roads, the Florida "Greenbook" provides for 4foot/5 foot bike lanes as a design and engineering standard, but that's only a guideline and may (depending on local law) not be absolutely binding on the municipality.
The "bike way" definition was explained by FDOT in their report to the Florida Legislature:
http://www.dot.state.fl.us/safety/pe...xecSummary.pdf