The category of operation bit was addressed by a circuitous route in the ANOs. I don't have my archive copies with me so I won't try to recall the exact spot to avoid getting egg on my face when someone jumps up and tells me I quoted an incorrect reference. If you need to know, I can dig it out for you in due course. Or else you could give Nev Probert in Canberra a call as he would recall the reference at the blink of an eye.
There was a single note in one ANO which required that the heavies were certificated in Transport Category, so the question of RPT throught PVT was irrelevant. In addition, CAA, DOT, DOT-ATG, DofA, CASA (or whatever letterhead you might choose from day to day) would not, in reality, let you fly a serious heavy in other than a manner equivalent to RPT, eg recall the Associated Airlines operation.
The contaminated runway requirement was imposed by 20.7.1b in which a clause required the operator to do some unspecified thing to address the problem. The usual mechanism was to go into written dialogue with the regulator and arrive at an understanding. The same sort of thing applied with runway lineup allowances - the original letter was to QF in respect of their big bird operations. I have that somewhere in the filing cabinet. I suspect that that reference still binds the operators to doing something useful in respect of contaminated runway operations.
Do keep in mind that the tech people in airworthiness and operations weren't the originators of many of the changes in recent years.... they often were vigorous opponents but were drowned out in the cacophony.
I have a reasonably pertinent background in the area in Australian operations and there are a few others in the ops engineering area who can throw some historical light on these matters.