G'day tosin, welcome to GPS Power.
Patched firmware is not needed for Montana 610 to use unlocked NT maps. It's firmware has MSV but not GSV which means it's not protected by software verification, but because it has map signature verification you cannot successfully use maps unlocked with FIU [Fast Image Unlocker]. To overcome the MSV you must use only latest version of [Only registered and activated users can see links. ].