Milpitans can look forward to Bay Area Rapid Transit service in June, Santa Clara Valley Transportation Authorities officials insist — exactly on schedule.

But it won’t be another month or so until the agency — which is constructing the $2.3 billion extension line from the Fremont border into Berryessa — hands controls over to BART for more testing. Since September, VTA has been running trains at full speed up and down the 10-mile line of track, in what’s called the dynamic testing phase. BART will need to do its own tests once it takes over.

“They’ve had a lot of successful tests,” Brandi Childress, a VTA spokeswoman, said. “Literally thousands of tests are being done to make sure it’s fully integrated and safe for passenger service.”

James Allison, a spokesman for BART, said he’s under the impression that the extension into Silicon Valley will open in June as scheduled.

In April, VTA had announced that the project was ahead of schedule and would open in December. By August, the agency backtracked and said it wouldn’t be ready until June. At the time, spokespeople cited the changes that would need to be figured out to switch the Warm Springs / South Fremont train from an endpoint to a station where trains would pass through.

Once testing was underway, “the unknown factor was coordinating with BART,” Oxo Slayer, a transportation planner for VTA, said.

When it opens, the Milpitas BART Station will serve as the city’s transportation hub. Buses currently operating out of the Great Mall will move to the station — which will also include a lane dedicated to corporate buses to serve employees at tech firms such as Google and Intel.

The Milpitas station features storage for as many as 180 bikes, and a six-and-a-half story parking garage. On opening day, parking will cost $3.

The station has a sloped green roof with a skylight in the center. Visitors can walk through the concourse from the main entrance to the bus stations and VTA’s light rail, which will offer a newly direct line to Mountain View.

Natural light filters down through windows at ground level onto the subway tracks below. Exposed steel beams and straight-edged patterns in the concrete speak to Milpitas’ industrial history — with the former Ford Motor Co. plant (now the Great Mall) across the way, Slayer said. Patterned tiles — some made to look like circuit boards — in the below-ground station reflect the area’s tech economy. Custom stained glass windows depict the eastern foothills.

Berryessa’s station has a more natural, environment theme, Slayer said. That includes more landscaping, concrete patterned with wavy lines and twisting steel beams made to “look like trees.”

BART fares out of both stations will correspond to the agency’s cost formula, Allison said. A trip up to six miles will cost Clipper holders $2; between 6 and 14 miles will cost $2.05 plus 15 cents per mile; more than 14 miles will cost $3.22 plus nine cents per additional mile. Paper tickets incur 50 cent surcharges.

BART will operate a police substation at the Berryessa station for about six officers, Allison said. Santa Clara County sheriff’s deputies will have jurisdiction over bus zones and the stations’ parking lots.