I guess the answer to your question is yes and then again, no.
Yes in that if you have learned the piano, you have also learned the keyboard as far as chords, progressions and theory. The two are the same in that respect. THe sustain pedal also has the same function on the keyboard and piano.
The answer is no in that some keyboards have 61 keys, 76 keys, and 88 keys . . . and other combinations. Keyboards have different voices that must be mastered . . . electric piano, piano 1, 2 and 3, guitar voices, etc. Some keyboards have rhythm. Some have internal speakers, some must have an amp. WIth keyboards you should know MIDI use, programming from a PC, a bit of technology. And of course, keyboards are great because they are portable whereas pianos aren't. However, it is great to have the wieghted piano keys, and weighted keyboards are a tad more expensive.
So I would say both have advantages and disadvantages. Some keyboards sound as good as any organ, and they are portable . . . . so a keyboard may be a good investment, even if you do have access to a piano.
Be Blessed . . .