Why is it されてる and not されている？

Question

Is the verb used here される？ Is the progressive form often shortened to remove い from いる？

Answer 1

Yes, as you thought, 案内されてる is a shortened form of 案内されている, a combination of the verb 案内される in te-form + the subsidiary verb いる. When people use いる as subsidiary verb, い is often dropped although people regard it as casual spoken language.