I don't think so, the chiebukuro link talks about confusing itameshi for ita(me)meshi. I'd like to see some actual evidence of itameshi being used with this meaning first.

https://detail.chiebukuro.yahoo.co.jp/qa/question_detail/q118298901 (from 2006)
Q: “イタ飯”ってイタリア料理の事なんですか？ チャーハン（炒飯）だと思ってました。
A: きっとまだお若いんですね。バブル全盛期にフランス料理より軽くておしゃれーと大流行した時の呼び名です。イタメシであって炒め飯ではないのです。

I was mystified by your comments until I found the quoted chiebukuro Q/A. It seems it's confused with 炒め飯/いためめし. Not sure we should be adding it as a here with a "confused with" sense? Or perhaps a "いためし" irregular reading put on the 炒飯 entry?

Not sure how to handle this in (add this to) JEDIC, but there is also a Japanese version of "itameshi" that is unrelated to Italy: 炒飯 (in Okinawa called "chaahan", from Chinese "chao3fan4"). A local NS informant tells me that many call it "yakimeshi" 焼飯, but I cannot vouch for the two terms having the same connotations (it is likely that there are regionally different ingredients and regionally different ways of making the end product that could lead to different terms being used).

Not really an abbreviation. Daijs just has "《「イタ」は「イタリア」の略》イタリア料理。"

@@ -16 +16 @@
-<misc>&abbr;</misc>
+<xref type="see" seq="2403250">イタリア料理</xref>