Yes it does still occur.  The lady is put on payroll, deductions including, CPP and taxes are taken from the paycheck.  She receives medical and pension as outlined by the company.  She is on payroll like any other employee, though I have only encountered and heard of a salary pay.  A contract is usuaually signed outlineing the expectations (how many days a month and the hours which you are to be available).  As well, you are typically not permitted to ask the 'client' for any additional fees.  The lady will have a corporate credit card, and is to entertain the gentleman, with that card, in any way he would like (dinner, theatre, etc.)

I can't speak for the US, but it is much more common in Canada than I had ever imagined.  The pay is very lucritive (I've never been offered less than a six figure starting range), but I personally don't like the principle of working for somebody else.  When a company has that much money to pass off for 'entertainment' I worry that they won't be respecting my personal boundries when it comes to how they expect me to assist their clients.  I also don't like not having control over my own hours - for me, family always comes first.  And in these situations, the comapny always comes first.

As a side note, all of the places which use this arrangement have several ladies on their payroll.  A few remain independat escorts, but most are perfectly content with the fee arangement for putting in a few days a month for the company.