In round numbers, the electrification project encompasses ~2500 poles and ~3100 concrete foundations. The number of foundations is greater than the number of poles because there are foundations for guy wires and sometimes multiple foundations for portal poles.
The progress chart below will be updated monthly.
At the December 2018 meeting of the Caltrain board of directors, the program manager stated (starting at 01:03:00 in video) that he needed to maintain a pace of 156 pole foundations per month (six per night) to meet the schedule milestone of "electrification substantial completion," which was then set for June 2021. You can see how things went since then.