From BA.com:
Question
Customers travelling with British Airways from Newark Airport will be directed to a new Check-in area whilst major renovation work takes place within the Terminal building. This new Check-in area will still be located in Terminal B, but can be found on the ground floor at the central entrance.
Answer
There will be signs at the current Check-in desks informing you of the move and pointing you in the right direction, and the Port authorities will also provide roadside directions. The British Airways Lounge will not be affected by this renovation work and will remain in its present position.
The driving directions indicating the new check-in location are, shall we say, spotty. There are a few yellow signs indicating British Airways Check-in, but the large overhead signs for Terminal B also (still) indicate British Airways check-in at the upper level.
So if you're dropping someone off (or being dropped off), at EWR, drive (or be driven) to the lower level, as if you are going to Terminal B short-term parking.