Yes, the availability of emergency contraception leads people to engage in more risky behavior, because the availability of contraception allows people to participate in a behavior without facing the natural consequences of the behavior. If a person knows that there is a large chance of a consequences for a behavior, they will consider the behavior carefully. If the person does not think there will be a consequence, they are less likely to avoid the behavior.
Emergency contraception by definition is taken after the fact, so the risky behavior has already taken place. People already know the risks and are informed if they know enough to go get emergency contraception, so they have either made the choice to do what they want anyway, or had an emergency situation (hence the name.)