Present progressive meets past participle

I am trying to determine the verb-tense for the following sentence:

"If the worker is assigned to work for 1 year, they shall be given the standard longevity bonus."

On a practical basis, I see two ways to interpret this: (1) On the first day of work, a determination is made as to the projected length of assignment and that determines the bonus. This is suggested by the use of the past participle "assigned"; (2) the assignment length determination is continuously re-evaluated, and when it becomes likely that the assignment is for a year, the bonus will kick in. This is suggested by the present progressive "is" + verb form.

On a grammatical basis, is this considered to be a perfect past, a present progressive, another verb form, or simply grammatically incorrect?