See https://developer.valvesoftware.com/wiki/Prop_dynamic this will lead you in the right direction. In the properties, set Collisions to Vphysics.
your props on the map probaly doesnt got collisions models. that why they may don't have collision on because they don't have one. edit: for info set collisions to "use Vphyics" to enable collision to default (if they have) if they don't have any and you still want to have collisions then make your own collisions with brushes or select collisions to "use boundy box" but be careful the boundy box doesnt rotate with the prop and probaly won't suit the prop how it would.
