Yes, IP65 rated emergency lights can be fitted with emergency showers as the unit is protected against low pressure jets from all directions - limited ingress permitted.
IP ratings are comprised of at least 2 digits. The IP65 rating is broken down as follows:
6: Dust tight and totally protected against dust ingress
5: Protected against low pressure jets, from all directions - limited ingress allowed
Click here for a full explanation of possible IP rating values.