Buildcraft version: 7.99.7
Forge version: 1.11.2-13.20.1.2476
Link to crashreport or log (on pastebin or gist, please don't put the entire log here) : no crash
Singleplayer/multiplayer: multiplayer

Additional information:
Forestry version: 1.11.2-5.3.4.165
I'm not sure if I should report it here or at Forestry, but the main thing is:
neither does the engines nor does the kinesis pipes connect to the machines of forestry.

Forestry switched to RF, BuildCraft now uses MJ again

correct, forestry will most likely implement compat later once we reach beta and the api and mechanics are pretty much final

Thanks for the report! This is a duplicate of #3760