If a person work for Company A and gets laid off but then gets hired by Company B who is under contract for Company A. This person still performs the same work for Company A in the same office. After a few years, the person gets re-hired with Company A.

Is this considered a break-in-service under the ERISA statute?

Is company B leasing company? Did the person incur 5 one year breaks?

Company B and A a technology company, "break" was 3 years.
During this time, the pension plan in Comopany A changed.
Is this person eligible to receive the old pension plan from Company A?

Yes, as long as they were a participant in As plan when they left. In general, since they don't have 5 one year breaks you can't disregard prior service. Keep in mind the break counts only they don't have more than 500 hours in plan year. The break would be less unless they left on 12/31 and returned on 1/01.

Company A deied paticipant in the old plan (participent participate in the old plan for 15 years) and offered
a new plan because company A considered this 3 years as break in service and rehired employee geting
new plan.

What law describes 5 years ?

umike - before you spend futher time worrying about breaks in service, could you expand on your comment that Company A denied you participation in the "old" plan. I'm guessing that the company froze the "old" plan and installed a new plan. In that case, upon your rehire you would only be eligible for the new plan.

Could you provide more information about the old plan and new plan.

Yes company froze old plan, but partisapant was qualify to continue participate in the old plan by
grandfather rule when change was made. But when rehired company offered new plan.

If a person still performs the same work for Company A in the same office during this 3 yers,
Is this considered a break-in-service under the ERISA statute?