akdom

“Billy was to ensure that the computer was packed safely.”

Billy had been assigned the duty of ensuring that the computer was packed safely.

The [plan / agreement] was that Billy would ensure that the computer was packed safely.

It was [expected / arranged] that Billy would ensure that the computer was packed safely.

Also:

Mary is to present her report first.

=~ Mary is supposed to present her report first.

=~ Mary has been assigned the duty of presenting her report first.

=~ The agreement is that Mary will present her report first.

=~ It is expected that Mary will present her report first.

Employees are to wash their hands after using the restroom.

=~ Employees are supposed to wash their hands after using the restroom.

=~ Employees have been assigned the duty of washing their hands after using the restroom.

=~ The agreement is that employees will wash their hands after using the restroom.

=~ It is expected that employees will wash their hands after using the restroom.

The children were to take the bus.

=~ The children were supposed to take the bus.

=~ The children were assigned the duty of taking the bus.

=~ The agreement was that the children would take the bus.

=~ The arrangement agreed to was that the children would take the bus.

Sometimes the idea of duty is less prominent:

The president was to speak in Peoria yesterday.

=~ The president was supposed to speak in Peoria yesterday.

=~ Arrangements were made for the president to speak in Peoria yesterday.

=~ According to plans, the president was going to speak in Peoria yesterday.

=~ Because of plans previously agreed to, the president was expected to speak in Peoria yesterday.

is to, was to, etc. have to do with expectations we have which are usually formed on the basis of some unstated previous arrangements.

CJ