Rod Pullen, group CEO for the renamed agency, said the move would foster further collaboration between the two parties, which in the past had been limited to a handful of projects.
"We now see the likelihood to do more of that," he said. The move also creates a global profile for Red Cell, which already operates branded regional networks in America and Europe.
"It's tough to have a two-legged stool," Pullen said. "By joining in a more formal way it does complete a proposition."
WPP's Sir Martin Sorrell said the group saw Red Cell as a "creative and fast-moving agency".
The network is seeking to strengthen its Asian reach, particularly in India, where its operations are thin on the ground and Greater China, where it a stronger presence.
However Pullen stressed that agency ownership and strategy remain unaffected by the rebranding.
"Everything that Batey stands for, it will continue to stand for," he said, describing the network as a collective with a common goal.
Before the tie-up, Batey had already been reporting its financial details to WPP through Red Cell.