Such 'ai-to-wai' euphonic changes seem to be, to some extent, common in Japanese.
However, I'm afraid I really don't know whether someone around me is pronouncing 他愛 as たわい, 具合 as ぐわい, etc. As a native Japanese speaker, I think I can't even notice such 'ai-to-wai' euphonic changes in daily conversations. Someone more sensitive than me might have different impression about this.
One exception I can think of is Japanese family name 河合, which is definately pronounced as "かわい", and its correct furigana is even かわい.
(To make sure, correct furigana of 場合 is always ばあい, no matter how some people pronounce this differently.)
I pronounced "具合わるい" or "場合わけの計算" quickly for several times, and to my surprise, I found myself unconsciously inserting trace "w" sound before '-ai'!