In House Mechanic v Workshop Vehicle Maintenance

I am a logistics advisor for various countries in Africa, Middle East and Caribbean. Every country has a different standard of vehicle garages and capacity of qualification of mechanics. How do people decide in other organisations, which modality to use for vehicle and motorbike maintenance. Do you send it out to a dealer garage, a generic garage/workshop or do you fully set up a workshop in your own office? What are the various policies out there in relation to this decision making. The fleet we deal with is predominantly Toyota Landcruisers (Pick Up, 5 Door and 3 door Hardtops) and Yamaha/Honda 125 cc motorbikes (usually Dirt bikes or Agricultural models). Would be interesting to see if anyone actually have a way of making these decisions.