Yeah, that is also called "element stealing" ... not to be confused with track stealing ... but you can be confident that Real (and most other designers) almost never get angry about sharing elements (hence the NLDC stuff available), IF (BIG HUGE "IF") a designer would only ask first!!
with the mirroring...you could just use Tia's construction kit to mirror the whole track at once...but it messes it up so it would be pretty bumpy if he did that, and all the banking would be off.
Always please ask me if you wish to use an element Ive created. Ive never turned anyone down, it just keeps me aware of where my stuff is circulating.
You will almost never fool me on a peice of track. Wether its the whole thing, or just an element, I will know. I spend far to many hours on my tracks so I never forget them, at least, anything recent thats WORTH using...heh