What is the ETC equivalent of ICPB cues? And how do I use them on submasters...

ICPB being Intensity Color Position Beam?

not as general ETC rule but as Eos-Family rule:
Record will store every single parameter of each channel that has at least one parameter not at its home value anymore. the source of the value doesn't matter when you use Record (i.e. it doesn't matter if the value is in the "programmer" (which we don't have anyway), or from a cue or from somewhere else, as long as the source is not Park).

so as soon as you put your LED strobes at full and white and Record this to a sub, Eos will put not only the Intensity value and the color into the sub but also the strobe parameter and every other parameter those strobes have

ICPB being Intensity Color Position Beam?

not as general ETC rule but as Eos-Family rule:
Record will store every single parameter of each channel that has at least one parameter not at its home value anymore. the source of the value doesn't matter when you use Record (i.e. it doesn't matter if the value is in the "programmer" (which we don't have anyway), or from a cue or from somewhere else, as long as the source is not Park).

so as soon as you put your LED strobes at full and white and Record this to a sub, Eos will put not only the Intensity value and the color into the sub but also the strobe parameter and every other parameter those strobes have

the way ICPB faders work on other consoles (Mode 2 on Avo) is that let's say you have lights in blue, you want them to fade to red. With an ICBP fader, when you bring the fader up, the lights go from blue to red. When you bring the fader back down, the lights fade back to red.

Can an Eos console do this? 

yes, that's default behaviour. it's called Restore behaviour, it can be set to Minimum or to Background, default is background.

but: manual values ("programmer") cannot be background values, so: yes you can go back to the previous values by lowering the Sub as long as the previous value wasn't manual.