Alright, so I've scoured the web forever looking for a definite answer to this question and I hope someone can help me out in finally settling this once and for all..
I am a frequent user of MKV2VOB for my 720pmkv conversions to vobs, and I use TVersity to stream them to my PS3. I am under the understanding that this program takes 1080p files and converts the vobs to 720p. Is there someway of taking an 1080pmkv and converting it to some format with one or multiple programs that would result in lossless quality in the video and audio department and having it stream to the PS3 in all it's 1080p glory?
tsMuxer is what you need. Unless you've got some sort of weird subtitle file in your mkv (.ass, .ssa, .sub, etc.), you should be able to mux it straight to either m2ts (which doesn't support subs or chapters) or AVCHD/Blu-Ray (which does support subs and chapters).
Then, if you burn to Blu-Ray and aren't very keen on burning the resultant file to a DVD, you can use... AVCHD-ME.
I downloaded tsMuxer and ran a 1080pmkv of a TV ep through both tsMuxer (outputted to m2ts) and mkv2vob. I streamed both through TVersity to my PS3 and after watching a minute of each, I couldn't see any notable difference. A couple things could be a factor: my TV only goes up 1080i, and like I said these were 1080p rips of television, not a movie. Would either of these things matter? Is there some setting on tsMuxer I need to check out? Should I do the same test on a movie?
I didn't realize TV shows were broadcast in 1080p already. tsMuxeR doesn't change the resolution of your video, it is just a muxer. mkv2vob might though, I'm not sure.
Anyway, your best bet, to keep 1080i(p), is to use tsMuxeR to convert the mkv to m2ts, then watch that way. This will guarantee you keep the 1080 lines.
As an addition, I'd like to know if progressive scan/interlacing is determined more by the hardware than by the software.
Because from what little I remember about 480i/p, there is no difference between the "480" part of it - they both have 480 line each. The difference comes from whether a player (and/or TV) can support progressive scan or not.