Hi Tyson, 
 
Here is the issue I have. You say that you can tell whether a ETCS-equipped railway line is operating in Level 1, 2, or 3.  How  do you know it is an  ETCS-equipped line?  Your response would be that, "one can affirmatively
assert that a railway line is ETCS-equipped by pointing out Eurobalises/Euroloops."  How do you know that? This sounds like special knowledge rather than information I can pick up by standing next to it or looking directly at it. 
If I may for a moment look at CTC how do I know that that is by looking at the signals and shunts. Do I have special knowledge?   Yes, I do. Does this change your argument? This is what I was asking when I said. 

"If we can both assume that we both have extensive working knowledge of
railroads or railways and that we can identify correctly the system in
 use. Can we assume that we should be allowed to map it if we can look
 at the ground and see that it is what it is? Or do we need to make the
assumption that we don't have a working knowledge of railroads or
railways and that we need to assume a role as an outsider when mapping
railroads and only map what we can see (signals, switches, balises,
magnets, contacts etc.)?"  

  I will agree that understanding if you are looking at a CTC line or not is a specialized characteristic of a mapper. And I will also assert that understanding if you are looking at an  ETCS-equipped line and Level 1, 2, or 3 is also a specialized characteristic of a mapper.    

Be Careful about the use of terminology as it may not be the same. I will not assume that the OCS that you are using here means Occupancy Control System as I found a completely different meaning on Wikipedia. 

 I would be the first to agree that Train Protection in this context primarily aligns with PTC as I described in my previous email:
" Here in America what you are describing in train protection is Positive Train Control (PTC). Positive train control has GPS based land stations and locomotive GPS attachments and hardware. "  ACSES is a specialized version of PTC and not wide spread here. I had to look this up to find this out.

I think we can both agree that the detail in your statement is too much detail for OpenStreetMap "(And the signs don't count, because they could simply be overridden in Special Instructions (or the US equivalent). Moreover, there are no signs that differentiate -- for example -- siding control territory (SCT) from CTC sidings in Canada.)" Your statement is like saying we should not map the seasonal roads as they could be closed.  Seasonal roads here are tagged as "access:conditional" rather than leaving it without a tag. Of course those tags are general and not specific and the road department can close the road or make it one way at any time.  

In your statement: "While signs for these exist (in some locations), they are not properties of the railway line itself: rather,
they are properties of how movements on the railway line are conducted." So what is ACSES, ETCS, and LZB? 
These are not descriptors of the line; these are descriptors in your words of wayside equipment (Eurobalises/Euroloops, balises, and signals)  attached to a system of train protection for train moments.  I would conclude that "they are not properties of the railway line itself: rather,they are properties of how movements on the railway line are conducted." 

Are these two arguments clear?
OpenStreetMap is not an ideal place for a lot of the railway data we want to add to OpenRailwayMap. I would reconsider the use of "Signalling" to "Train Protection" on OpenRailwayMap, if your argument stands. Signalling is train movement. 

Cheers, 
Nathan P

Reference: 
As*sert 
verb
  1. state a fact or belief confidently and forcefully.
    "the company asserts that the cuts will not affect development"