politeness - Using 尊敬語・謙譲語 but not 丁寧語 on the same target

I was reading this passage from 下町ロケット (pp 15-16):

{{pad}}「申し訳ないなあ、忙しいときに来てもらって。というのも、今日は折り入ってお願いがあってねえ」
徳田{とくだ}は、トレードマークの鷲鼻を指でさすりながら、佃{つくだ}にソファを勧めた。新しい会計年度がはじまって間もない、四月第三週のことである。
品川に本社がある京浜マシナリーの応接ブースだ。青色のパーティションで仕切られた個室は、四人がけのテーブルと電話が一台あるだけで質素だった。一部上場企業でもある同社は日本を代表する機械メーカーで、佃{つくだ}航平{こうへい}が社長を務める佃製作所の主要取引先である。佃は売上の一割近くをこの京浜マシナリーからの下請け仕事で賄っていた。
「実はね、佃社長にわざわざお越しいただいたのはウチの調達方針が変わったことをお伝えしようと思ったからなんだよな」

「方針変更、ですか」
佃は身構えた。
なにしろ、下請け苛{いじ}めともいえる厳しいコストダウンで知られた京浜マシナリーだ。

I noticed that 徳田 is using both 尊敬語 (佃社長にわざわざお越しいただいた) and 謙譲語 (お伝えしよう) to show respect to 佃, but otherwise his language is pretty rough and informal (あってねえ、なんだよな）. This is the first I've seen this, and I'm wondering in what circumstances it happens.

I have two theories of what's going on in this excerpt:

1. 
   

   Since 徳田／京浜マシナリー is the お客, that already puts them in a relatively higher position. On top of that, I imagine 徳田 is probably a much older guy. Normally I think this isn't enough to warrant dropping 丁寧語, but I could see it perhaps happening. But in this case, I don't see why 徳田 would continue to use 尊敬語 and 謙譲語 really...

   
   



2. 
   

   As mentioned at the end of the excerpt (and a little later), 京浜マシナリー do not seem to be very nice people (especially given that what they're doing here is probably a violation of the 下請代金支払遅延等防止法). So, maybe the lack of 丁寧語 is being used to drive home the sort of rough nature and power balance of the interaction. In this case I'd imagine the 尊敬語／謙譲語 is being used a little sarcastically (not completely, though).

   
   

I'm not sure that either of these theories is correct... it could be something else. What's going on in this passage? More generally, in what cases does it make sense to not use 丁寧語 but use 尊敬語／謙譲語 all on the same target?

Answer

I feel the あってねえ/なんだよな part reflects the 徳田's true attitude toward 佃. Unless 徳田 and 佃 are close friends, 徳田 is speaking in a disrespectful manner as a business setting. He is being highly dominating, knowing his company is stronger.

わざわざお越しいただいた/お伝えしよう is used here to show 佃 a "respect", of course. 徳田 intentionally used these minimal 敬語 because he knew he was going to make a difficult request, while he wanted this contract to look legitimate.

In general, when a person who speaks impolitely suddenly starts to speak politely, you can anticipate something bad follows :)