'The materials must be (1) in the facility/station doing the producing or (2) in facilities/stations that are (a) loadable facilities in the city* (See Mining: Storing Materials) or an adjacent space station and (b) are operated by the producing facility/station operator, or the person starting production, or are managed by the producing facility/station manager, or are owned by the producing facility/station owner.
* This may change to only adjacent material loadable facilities in the future. '
It's been a few years since I did this, and while I'm moving a shit ton of RMs, I'd like to know if this is still true.