Air carrier inbound to EWR voiced concern regarding the lack of RVR information being provided by the ZNY controller; alleging subject information is necessary prior to being transferred to the Approach Controller.

Narrative

ATIS at EWR had been reporting 1/8 miles; 200-300 FT overcast. Prior to descent we asked if they were flying approaches because weather appeared below minimums. We asked Center to verify the actual weather that let approaches continue. We said based on ATIS the field was below our minimums. No RVR was reported on ATIS. The Controller did not help; only stated it if it below your minimums we will have to hold you. Based on FAR/AIM US 7-1-33; the Tower is required to report RVR when it is below 6;000 FT. This is a trap because even when weather on ATIS is reported below minimums; we have to descend and wait until we are turned over to Tower in order to see if we're legal for approach. This is too late in the approach phase. On this particular approach; the First Officer had to request the weather information just prior to FAF to confirm our legality. We received extremely poor ATC service during this flight. There should be some mention either by Center if asked or some mention on ATIS as to RVR to give us a better understanding to field conditions. I understand why a constant RVR update cannot be made on ATIS.