Railcraft_1.7.10-9.8.0.0
forestry_1.7.10-4.2.4.52
What I tried so far:

• right clicking with a stack of capsules on a Coke Oven
• placed a stack then a single capsule in the Coke Oven slot
• filled a Forestry Bottler with creosote and tried the capsules there

Sooooo... all the Forestry capsules are called "Forestry:waxCapsule" while the Railcraft one is "Railcraft:fluid.creosote.wax". Buckets and bottles filled with creosote work fine with all Forestry machines. Capsules do not. I am also reporting this on the Forestry GitHub.

Will be fixed when Railcraft switches to Universal Fluids, per #996

This is the way you are supposed to use it.

I can verify this, 9.8 it worked fine, once 9.9 or 9.10 it doesnt work.

Forestry versions 4 to 4.2.11.59 all worked with Railcraft 9.8, there a config fix or script fix we can place?