Your time spent in the US without working (except for short visits for business or pleasure in B-1 or B-2 status), or while working for an unrelated employer, do break the one continuous year foreign employment requirement, but should not affect the three-year period. The relevant point in time to satisfy the 1-year foreign employment requirement is the date on which the initial L-1 petition was filed, regardless of when the worker was or will be, admitted to the US.