On initial approach to EWR; the flight crew of a turboprop commuter aircraft complied with a TCAS RA with a TEB departure.

Narrative

As we were descending to 2500 FT and direct GIMEE preparing for the approach into EWR; ATC instructed us that an aircraft was departing TEB and would level at 1500. Our TCAS issued an RA; which we complied with since clouds obstructed visual contact with the other aircraft. I notified ATC we were deviating due to an RA and were climbing again. He said OK; and that once we were clear of conflict to join the Localizer and descend back to 2500 FT. He said it's OK if we go through the LOC if necessary. We cleared the conflict very quickly and started descending to 2500 and joined the LOC from the other side. We were cleared to descend to 1700 FT and cleared for the approach. It was a high workload time but we were able to achieve a stabilized approach. We completed the approach with no further problems. ATC did warn us that there was an aircraft departing TEB and that he would level at 1500 FT; but since we got the RA we decided to comply just to be safe since it was too cloudy for a visual identification of the aircraft. In visual conditions it wouldn't have been an issue but in IMC it would be better to space arrivals to EWR and departures from TEB so that situation won't occur.