Muxing Sub and Idx files into MKV?

[ShadowFX]

I have a couple of files downloaded: OGM file, Sub and an Idx file. Now I know it's impossible to mux those VobSub files into an OGM container but can it be done into MKV containers?

I am familiar with MKVToolNix but after it looks okay when muxed it doesn't show those subs. I have the latest VSFilter 2.33 installed. Everything else is also in working order.

Just need to know if this is possible or not.

[unmei]

It is possible. With MkvMerge, as you thought right.
I have never tried it as i'm more into text subtitles, but from what i know it should be quite stable/reliable by now. However i don't know if there are special restrictions on the SUB.
One i could imagine is that you have to unrar the file - it will be compressed inside matroska anyway, but with a different compression scheme.
If your subtitles work outside of matroska and you cannot figure out why they do not when muxed, read up in this thread (http://forum.doom9.org/showthread.php?threadid=64548) (and if you still cannot get it to work, talk to Mosu).