Try Chippenham - Bromsgrove in a booking engine with a via point of Birmingham New St added. I don't think there's any engine that will show the easement allowed journey opportunities. Not coded.
Try Westbury - Newbury with a via point of Reading. Many/most booking engines will show the easement allowed journeys. Coded.
My use of that versatile word "coded" may have been confusing.
The NRG data feed includes easements, and it is expected that routeing engines will understand these and implement the easements. No software changes (i.e coding) should be required.
The data format can represent almost all the easements wa can see in the text file, and that includes the relevant one (700351). There are some easements that contain elements that don't map onto any of the definition records, but I have no idea whether these words are really needed (by machine or human) or just there because.
There is no way in the data feed to indicate that an easement exists but cannot be represented in the file. The format of the readable text is undefined (except as "free text") so is not a substitute. Of course the data feed may not be complete or self-consistent, but there's no identified source of "additional definition information for humans".
That leaves the question of whether the routeing engines actually implement all the easements correctly. I think we all know that these are big complicated heaps of software, and all of them give the wrong answers at times. The most complicated bits of the fares/routes/timetables system are where the errors arise, and easements are complicated to deal with so it's no great surprise they aren't always allowed. What's harder to say, or even to guess, is whether the software should cope but fails, requires some human help (e.g. to tweak data tables rather then reprogram) which is lacking, or this was never part of the design but was accepted as a shortcoming to be incorporated later (and may or may not ever be).
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