If the greenhouse uses normal soil then ofcourse it's not totally isolated, but still i'd expect them to use less
There's usually bugs. It's common to deliberately introduce predatory insects, which control the pests in the same way as in nature, with the additional benefit that they can't fly away if the pest population gets too low. Chemical pesticides are also widely used, both organic and non-organic.
Hydroponic crops are especially vulnerable to sucking pests (aphids, whiteflies, etc.), because of the large amounts of tender new growth. Without controls or natural predators, their population can just explode, much worse than anything you'd get outdoors.
Thrips, white flies, and other insects are _very_ common.
ETA: to add info for you. CE usually implies the control is from inputs (water, nutrients, light) not physical access.