On the LAM3A arrival, the only restrictions published - to us at least - are at Logan and Saber (off the top of my head) at F250 and F150 respectively, which are actually slightly above the ideal descent profile for an A346. We, and probably most other long haul operators, have quite a few canned routes from the Far East, and there's no way of knowing which one you're going to get until you turn up at the aircraft. As you say, any other tactical restrictions aren't published to the crew, and the CFP is obviously going to be generated up to 18 hours before our arrival in the area in question, by which time everything may have changed anyway!
We can and do generate higher fuel minima for factors which we know will cause problems, and certain arrival times at EGLL fall into that category, but we'd be reluctant to make a ruling that we should carry extra fuel in case tactical restrictions exist. You could generate reasons for extra fuel ad infinitum, and it costs a lot to carry the stuff 6000 miles to find you don't need it!
In any case, whatever rules or procedures you make, there will always be an occasion where some flexibility is needed. All we can do is plan for, say, the 95 percentile scenario, and trust the crews to use their experience and charm to cover the other 5% when the plan doesn't work as advertised. It will always be thus, I fear!