I have heard this grammar used a lot right at the point where the speaker gives up in a hopeless situation. Simlar to saying "Even if ... it's too late."
The sentence usually ends in 〜ない or words such as 無理だ or 無駄だ。
blabby
updated. tnx. :)
eastmael
ところで also means "by the way" which you use in trying to change the subject. ところで、あの件はどうなったの?
bamboo4
The 'た' can be from any past tense verb so it could equally be だ from 読んだ and such.
Paul
What's the difference between this grammar and ~ても (~te mo)?
yookoso
This is listed as JLPT L2. However, it wasn't included in my L2 test book. I first saw it in my N1 grammar book.