After two tests and a lot of feedback from the community, Blizzard has reintroduced the same faction Battlegrounds and plan to leave them up for the remainder of the expansion.
With a change that went live with the weekly maintenance that saw patch 2.5.2 content uploaded to live servers as the first look at phase 2 before the new raids open in two weeks.
Premades will be restricted again to a maximum of 5 players, however, this won't be in forever, as the development team is looking to explore other options.
During the second test, Alliance players were awarded an enlistment bonus for queuing Battlegrounds however, it does not seem to be in the game this time.
Burning Crusade Classic Same-Faction Battlegrounds Are Back And This Time For Good
"Along with scheduled weekly maintenance in each region, we’re re-enabling same-faction Battlegrounds. A same-faction Battleground will now occur when an opposite-faction match cannot be made after a short time. We currently intend for this system to be in place for the rest of Burning Crusade Classic." Community Manager Kaivax said on the forums.
The post also hints at "long-term plans for pre-made battleground groups", which could mean a system that pairs pre-made vs pre-made against each other.
While many may not like the idea of same-faction Battlegrounds, horde queue times need to be adjusted and Blizzard has seen this system as the most effective way to make a change.
It is likely this system will be looked at before going into Wrath of the Lich King Classic servers.