Maintain PR Status - Exception to the 730 day rule

Dear All,

"IRPA establishes residency requirements and obligations with respect to each five-year period
after the granting of permanent residency status.

A permanent resident complies with the residency obligation provisions with
respect to a five-year period if, for at least 730 days in that five-year period, the permanent
resident is physically present in Canada, or:
.....
is outside Canada employed on a full-time basis by a Canadian business"

The above has been quoted from an official CIC document.

My understanding from these statements, is that; as long as you are employed by a Canadian business you can reside out of Canada and you maintain the PR status.

I would like to start a discussion on what this means for people who have applied for PR and do have jobs in Canadian companies overseas, with either branches, subsidiaries or the parent company itself.

1 - What documents need to be shown to the Canadian immigration to prove "employment by a Canadian business"? - Are tax returns enough?

2 - Do these individuals need to pay Canadian Taxes?

3 - When, where and how is the determination of permanent residence and renewal of status done?

I would like any knowledgeable individuals to shed some light on the above topic.