My understanding of greenlanes is that they are part of the legal road network and are classed as BOATs or Byways Open To All traffic as they have vehicular rights. In order to drive them, all of the road laws and regulations still apply, ie tax, mot, insurance etc are still required, however as it is still the road network insurance companies would find it difficult to say they wouldn't insure you on them (although most still try to until you challenge and educate them).
