Accommodation provided taxation

[risky]

When discussing taxation, rental allowances paid in cash seem to be taxed as normal income, while rent paid directly by the company is taxed at a concessional rate. If my company is willing to pay some of my rent, but not all of it, how can that work in practice? e.g. Would they deduct $x per month out of my net salary against the rent they pay? I'm just trying to work out how the following situation from IRAS works in practice:

The taxable value is:

(1) The lower of:

* 10% of employment income, or
* the annual value of the premises

(2) Less rent paid by employee (if any)

(bolding mine)

It seems that even if the employer pays no subsidy, but if they are willing to allow the employee to "salary sacrifice" the rent (e.g. report a lower salary, but pay the rent direct and declare both) then it can save significant rent. But is that kind of tax minimisation legal?