100% just drop it behind you as you exit the tram. Way better metal container for blasting.
"Counter-terrorism" just means nobody thought about it more than 2 seconds or else they'd have a more specific reason.
While I'm not intimate with the difference between British English and American English, I'm pretty confident "Truck Bomb" does not mean a bomb inside a rubbish bin.
But yes, vehicles are a great vector for terrorism and I'm honestly surprised at how few instances there are of people just running other over. But it's also one of the reasons in the US basically every government building has large concrete planters around them (can't ram a truck through it).
Weirdly, bins were never removed from train stations in Northern Ireland. Bin bombs were never really a thing there, it was generally easier to shut down the railway by setting something on fire at a level crossing (often a hijacked police landrover)...