Asbestos actually comprises two distinct mineral types:

Chrysotile
- White asbestos, is actually a form of serpentine
- Short fibes, used in asbestos-cement products
- Dissolves readily in lung tissue (2-12 months)
- Treat as with any other inhaled dust (all dust is harmful, be it
household, diesel particulates, MDF or hardwood cutting)

Crocidolite
- blue/brown asbestos from amphibole group of minerals with completely
different crystal structures and chemical properties.
- Very long fibres, used in lagging, bulk insulation & fabric
- Does not dissolve in lungs, permanent, causes mesothelioma
- Not used for house soffits, garage roof or walls in recent periods

There is no requirement for specialised contractors for Chrysotile,
but realise companies can do the old woodworm trick "pulling dust out
of their pocket from elsewhere". They may quote low to get in the
door, but then miraculously the bill escalates - until insurers
question the 20,000 bill and suddenly find the alleged board did not
exist in the house.

Chrysotile boards are a simply fantastic insulator re solar gain (and
fire proofing), and the garages are usually extremely well ventilated
re drying from the roof panel corrugations and any door gap.

The easiest to remove are the J-bolt fitted roof panels - pretty much
bolt cropper the J and slide off. Realise however the panels are
brittle (do not walk on) and the steel frame is typically very weak
with the chrysotile panels themselves providing a surprising amount of
bracing. Many local councils will take chrysotile double bagged, but
not all. It is quite possible to dismantle a panel at a time and
replace with various agricultural boards so you have a migration over
years. Worth doing, but beware the panels may be supporting a fair
amount of load if the frame is heavily corroded. You are more likely
to be injured by the thing collapsing. Do not angle grind basically.