xhonzi said:

So... how do I get this onto my PS3 short of a BD burner?

Use tsmuxer to remux the m2ts to a ts. (You will need to mount the ISO with Virtual Clone Drive, if the download be an ISO, and pull out the m2ts file.) MKV2VOB will accept the ts as an input, and break it into chunks without trancoding.

Configuration--> File Splitting --> FAT32

There will probably be about a dozen files, and I believe people rarely break files this big, but it should work. This approach could be used if you want to literally put the BD-50 onto your PS3: otherwise, you might be able to stream it, but I have no experience with streaming, so perhaps somebody else could advise you on that.

N.B. When you load the m2ts into tsmuxer you could take the opportunity to ditch any unwanted audio tracks. That should reduce the number of chunks if you do choose this route.