To my knowledge, the transfer of soluble apolipoproteins between lipoprotreinas is simply mediated by their differential affinity for lipid content thereof (sharing)

It is affinity mediated mechanism. ApoE can bind more preferably to chylomicrones when come closer to HDL. Most probably due to receptor on chylomicrones for apoE. because ApoE itselp is a protein and chylomicrones have a receptor for it.

thanks dear Gerique, your answer can explain it. literature is very weak about to answer the question. the transfer is through simple diffusion, a manuscript says. i think there is no an exact answer. my opinion it might be electrostatic interactions that drives apolipoprotein transfer from one to another. specific amino acids on apolipoproteins or lipid molecules or lipid-protein interactions might also be responsible for it.