They've pulled this before in the commuter train station in Chicago.

Right, Spain already does this. And I've during high-profile events I've seen TSA patrolling the main subway stations in Washington, DC.

I've been travelling all around Spain for the last month and I wouldn't characterize the Renfe/AVE security as anywhere near the TSAs. You basically just put your bags through a machine and get waved through, and I've yet to wait in much of a line.

Yeah, same thing for the Eurostar, it's a much saner security and check-in process. As much as I love flying, I always take the train from London to Paris or between Madrid and Barcelona.

I nearly lost a pocketknife when my suitcase was x-rayed at a Spanish train station.

Our small satchel bags and bodies did not get x-rayed, but the large suitcases did. I forgot I had a pocketknife in there (as it's fine usually for airport security as a check in bag). Somehow, when my suitcase got scanned, they mixed up the order and the person behind me got stopped for having a knife. By that time, I was making a quick getaway to the platform as I didn't want to lose the knife.

I could have just had a knife (and bomb?) in my satchel bag, so was pretty confused by the whole x-ray suitcases only situation.