It's called SHARED SYSTEM ACCESS (SSA), a parts dept. is an ideal use for this feature. It gives multiline/station access like the old 1A2 KTS. This way you can pickup and HOLD from any phone that has the appearances (You can see the lites <LEDs>) and know the status and amount of calls.
One of my clients is a car dealership, the parts originally had only a cover button for the "parts line" appearing on the sets. The parts manager hated this setup. When they remodeled, they added more phones and hence exceeded "cover" capacity. I explained how the SSA would work and he said change to the SSA post haste. Changed all the parts phones to MLX16DPs. He was told when the Legend was installed (by Avaya) that it would not do the multiline arrangement... Consequently, he is happy now!
....JIM....