The construction site of a new station, that JR are progressing between the Yamanote and Tamachi stations with the aim of a 2020 completion, was opened to the press for the first time.
I'm struggling with the part in bold. If I'm parsing this correctly then the simplified relative clause will be
My problem is that 進める already has a subject (ＪＲ東日本) and an object (建設), but I thought 駅 would be the object.
My only guess is that を isn't the object marker here but means 'through' (like the use with 歩く for example). So the clause would read 'the station that JR are progressing through the construction phase.
Am I correct or have I made a serious parsing error?