The plot below shows my trek along the BC&F grade. I approached the grade just north of Twin Buttes and followed it up and around the big loop. Once around the loop I explored some of the old stone building remains. After that I climbed up on top of the tailings and explored some of the small bits of hardware lying about. I spotted a few smaller spikes in addition to the normal spikes. I'll post some of the more interesting photos for your enjoyment.
One thing to note is that there are lots of signs indicating that this is state land on the upper part of the line. I started my hike at the dirt parking area on the lightner creek road. The signs indicate that the area is off limits until about mid July to avoid disturbing the Falcons. Just beyond where I approached the grade is a gate to keep motorized vehicles out.