I've had quite a few files resume in 4.9.33 (and earlier).
I've had lots that don't resume.

I just depends on whether the host is available, still has the file, and isn't too busy.

Take a look at the graphs at http://www.limewire.com/english/content/netsize.shtml

There are a million people jumping on and off the network (even though the stats are not very reliable just now).

Just my luck to get part of a file from someone who is jumping off