Can Regular Expressions Be Safely Reused Across Languages?

Yes, there are differences in how different regex engines work - anyone that has ever used regular expressions in more than one programming language will already know it. Yes, this impacts what text matches and performance.

And yes, many programmers don't care or don't want to waste time on it (be it learning regex properly or thinking about a suitable expression for their requirements) and so just copy and paste expressions from elsewhere without caring too much about compatibility or performance. (Sometimes it is justified - "don't reinvent the wheel" and "premature optimization" and all that.)

I personally don't think we needed a paper or study to tell us this, but if it raises awareness, then I guess its a good thing :)