One-off missions? never.
A regular ongoing campaign? All the time.
It's only available on the Boomerang Spotter Plane, the Lexan Surveilance VTOL, and the SeaBuster Strike Fighter, but it is an essential part of battle information for any mercenary force IMO. Each of those units are still only close to 2 million C-Bills, with the cheapest -- the Boomerang Spotter Plane -- being less than 85,000 c-bills.
If the Boomerang saves you only a ton of armor by not being surprise attacked only once in its entire lifetime before being shot down, it's almost paid for itself right then and there.