I know there was some code for CI+ by someone but it's incomplete and based on old TVheadend version.
But atleast non-paired channels should work fine in TVheadend.
You could add paired channels from a Enigma2 box as IPTV stream and get all channels in TVheadend that way.
But that solution needs 2 cards or a cardsplitter.
But since it works with all Enigma2 boxes i know of i think Comhem's CA modul work in CI mode only so with a card paired to their CA module seems to be enough for now.
Multiple channels with a CA module that supports it works after this commit in 4.3 development versions and someone comments that 6 channels works at same time. https://github.com/tvheadend/tvheadend/pull/1090