Evidence seems to suggest it is:

Trade between the EAC countries almost doubled from $2.2 billion in 2005 to $4.1 billion in 2010, although regional trade with the rest of the world expanded faster, meaning that the relative share of intra-EAC trade has stayed around 21 per cent since 2005 [The African Average is 11 %]. “Europe enjoys 64 per cent internal trade; our 21 per cent is better than we thought, but we have to make efforts to do better,” said Betty Maina, chairperson of the Kenya Association of Manufacturers.

Kenya still remains the biggest economy in the region, although some convergence is definitely likely to happen in the next decade or so given the large hydrocarbon discoveries in Uganda and off the Tanzanian coast.

The region’s oil consumption rose from 96,000 barrels per day in 2003 to 144,000 barrels per day in 2010, with Kenya consuming more than all the other EAC countries put together. East Africa now accounts for 10 per cent of all mobile subscribers in Africa, with the number of mobile subscribers surging from just three million in 2002 to a staggering 64 million in 2010.

More on this here.