The fact that it is a 2-of-2 multisig is relevant only because the UTXO - that is actually the channel - must be spendable only if both parties agree on that or some other conditions are verified (like in force closure).
The onchain broadcasting actually happens automatically once you or the counterparty decide to close the channel, which can happen whenever you need to (that is the game theoretical assumption behind the security model of LN and the reason why it is actually a self sovreign protocol).

tolot

Xactly. My intermediate level of English doesn't give me a chance to describe what I want. 
I know that LN is 2of2 multisig under the hood. I wanted to know about opportunity to broadcast it

030e0dca83

lightning

Best way to obfuscate coins on Lightning?

kytt

I think you do not understand what is LN and how it works.
LN IS on mainnet. Is actually just not-yet broadcast onchain txs.