In my experience, the long spikes were used to secure the planks that run between and parallel to the rails where the road crosses the rail. No plates, just straight through the wood into the underlayment. Underneath the planks, the rail would usually be secured to the ties with the usual spike, plate, anchor system. There are more fastening systems in the rails than you can shake a stick at.
The shape of the head would seem to indicate a special purpose. My job was to secure the planks, so I don't know what the other guys were doing with those spikes. I know what I was doing with the round ones though, and the head shape is burned into the back of my eyeballs. The railroad union was very fussy about who did what back then. The guys using those spikes were probably making $5 more per hour than me. Nice thing about the railroad, at least in my experience, was that the less brute strength your job required, the more you got paid.
Ahh, the memories.
Nice barbeque f-stick though.