SHIRLEY -- Switching supplemental coverage the town provides its retired employees -- and pays half the premium for -- will result in savings for the town and retirees.

Selectmen received that bit of news Monday night from Jill Gallant-Shaw, senior account executive for the Massachusetts Interlocal Insurance Association, a health-benefits trust that offers services to communities that belong to the Massachusetts Municipal Association.

Gallant-Shaw and Town Treasurer Kevin Johnston explained the proposed new plan to selectmen in terms of comparative benefits and costs, including out-of-pocket expenses for retirees and overall cost to the town, with promised savings of at least $167,000 a year for the town.

After hearing the presentation and asking a couple of pointed questions, selectmen voted to make the change as recommended.

"I see it as a win-win for everybody involved," Selectman David Swain said.

Currently, the town's 50 percent share of Medex-3 premiums for 22 retirees comes to $633.85 a month, Gallant-Shaw said, versus $392.55 under the proposed new plan design, which consists of Medex-2 medical coverage and a PDP prescription-drug plan.

Gallant-Shaw said two-thirds of the retirees in the MIIA trust use that package, she said, adding that "it's a nice savings" for the municipalities and the retirees.

She said the town's bill would be even lower when new figures are established after the first of the year, and she expects to have those numbers available by next week.

Coverage is as good as under the previous plan, she said, adding that it's similar to the HMO offered to active employees and is only available to municipal groups.

"You can't buy it in the private sector," she said.

Gallant-Shaw said the new plan offers the same medical coverage as the old plan, with no network limitations or referrals needed, the same as now, so retirees can continue to see their primary-care doctors, choose specialists and go to any medical facility in the country.

The only change for retirees will be in prescription-drug coverage, with some co-payments where there are none now. On balance, however, lower monthly premiums should offset the co-payments, Gallant-Shaw said.

She said an MIIA team will conduct a presentation for retirees later this fall and will answer any questions they have about the new plan.