It's not as simple as plonking Plank in the official Mint or Ubuntu repositories and saying that it's done.
If I'm not mistaken, development of Plank is led by the elementaryOS developers, which means that agreements have to be made with them about distribution, licensing and what not before you can consider shipping it.
There's also the point that Plank is developed with the Pantheon Shell for GNOME3 in mind, so it would have to be tested by the respected maintainers of Mint/Ubuntu before it gets put into the respective repositories.
Problems? Tell us EXACTLY what you've done and what you expected to happen, IN DETAIL. That will save us questions, and we should get along better,
I have dysgraphia. This means I might have understood you incorrectly through no fault of my own.