Could the pump be configured so that Buildcraft (and by extension Railcraft) could pull the liquids out? Currently the only way is to use buckets. I realize that Buildcraft provides a pump, but the IC2e pump is much sleeker and already configured to run on IC2 Power, which means that Buildcraft is not needed at all. (I use Railcraft exclusively, which means I have to tank-cart all the liquids around. The liquid unloader should be able to pull water from the pump but it can't.)
The pump has upgrade slots... try building a liquid ejector upgrade and placing it in the pump. Then place a liquid loader next to the pump.
The pump should then detect the liquid loader as a valid fluid receptable and dump all its water into it.
A thousand blessings upon you.