Can holey metal furring channels be reused?
Assuming the base material hasn't been somehow deformed, buckled, creased, etc., adding several small screw holes to the existing ones will not materially effect the channel's suitability for it's intended purpose.

However, if you are improving someone else's property, and they are expecting new material in their work, using salvaged material would be quite sleazy. If this your own property, you will have no difficulties.