I am going cruiser captain, but I can pick heavy escort captain, and that gives me "attack pattern beta 3". Can I use that attack with my cruiser class ship?

It gives you the ability to train that skill, no? So you could teach it to a BOff, if you yourself are tactical.

And as to whether it'd be useful, you'd have to check if the high level cruisers let you use that level of power. If you know what tier the I and II versions are, III will be one higher. You can use the turbolift in the Shipyard in Sol Starbase to see what BOff slots the higher level cruisers are.

I think you've got some major misconceptions going on here.

The type of ship that you fly (Cruiser, Escort, Science Vessel) is not tied to what type of captain you are (Engineering, Tactical, Science). You can fly any combination of ship with any type of captain.

I assume that you mean "Attack Pattern Alpha 1", which is a skill that you receive at Lt 8 as a tactical captain. You can use this in whatever type of ship you choose to fly. Leveling up skills in for a particular type of ship only improves your ship's stats and handling for that particular ship (For example, maxing out Escorts has no impact on how well you fly a Cruiser, Science Vessel, or even the other types of Escorts, such as a Fleet Escort).

He's talking about the unlocked training abilities.

9 levels of Heavy Escort Captain, the skill, unlocks the ability to train Attack Pattern Beta III. Well, assuming your background is Tactical anyway.

No, i mean i am going all cruiser tier, but if I leevel up the one box in escorts called heavy escort captain, it gives a attack pattern beta 3, can I then use attack pattern beta 3 with my ship if im in a cruiser class ship?

it is tactical, so can i use the special command on my cruiser ship, instead of haveing to only use it on a escort?

You can't use it on a Cruiser because you need a Lt. Comm. Tactical Officer slot to use it and Cruiser only goes up to Lt.

Also, you need to be Tactical career to train that skill to your BO as well as maxing out Heavy Escort Captain.

you won't be able to train it unless you find a rare bridge officer with it.

You won't be able to use it unless you are in an escort with a lt.commander or higher tactical station.

By deciding to go cruiser you effectively say you do not want science or tactical stations higher than lt. but get lt.commander and commander ranked engineer seats allowing use of rank 3 engineer boffs.

This is completely separate to what your captain is and these seats do not change regardless of your captain type.