You should not participate in proficiency testing if your auto pipettes are not calibrated. Because there is a high chance that your lab failed in PT testing, which will reflect badly in your lab status such as credibility and accreditation.
Participating in a proficiency test should be used to improve the lab measurement practices, and not only a requirement. Once your measuring equipment is not calibrated, you do not have an important component to determine the measurement uncertainties regarding the lab´s method. Then, the PT will not be useful to improve the lab measurements.