Can you put pressure-treated wood and railroad ties in a dumpster?

Usually, with conditions. Pressure-treated lumber from a deck is normally accepted as C&D. Creosote-soaked railroad ties are a separate problem that many haulers refuse and some states regulate, so ask specifically rather than lumping them in as "wood". Confirm with your hauler before you load it, because a rejected load is billed to whoever rented the container.