To preface, I'm a big voice-line nerd and I think the voice actors did a fantastic job voicing the Operations squad for how relatively little lines they have. 

When I started the game last September I recall the Operations squad actually had dialogue talking about Titus' wariness of the Mechanicus during missions instead of their usual squadmate-to-squadmate banter. One complete campaign and 400 hours later and I don't ever hear these lines anymore. Are these voice lines actually tied to campaign mission progression? Can I hear them again if I restart the campaign with a new playthrough?

In that regard, I also noticed some bugged lines for the following Operations:

In Vox Liberatis the person who destroys the altar during the section where the mission switches from Tyranid to Chaos can say one of two lines depending on if the Chaos Sorcerer decides to show up or not. For example, Valius can either say "Onward to victory" if the Sorcerer doesn't reappear or "Altar down, now where is that Sorcerer?"

For whatever reason, Vespasius always says his line "Let us see how that sorcerer fares without his precious altar" even if the Sorcerer doesn't reappear. Scipius has the opposite problem where he only says the lines for when the Sorcerer doesn't come back.

In Ballistic Engine, every character makes a comment for when they the enter first shelter after the sandstorm. Valius however only seems to repeat a line he says when a sandstorm picks up. He says "Prepare for low visibility" when entering the shelter.

I assume these are either bugs or terrible RNG on my part but I was wondering if anyone had an answer for the first half of this post.