You can transfer a Help to Buy ISA into a Lifetime ISA, and it will qualify for the government bonus. The transferred amount will count towards your 2018/19 Lifetime ISA allowance.
Find out more about transferring a Help to Buy ISA to a Lifetime ISA.
You’ll need to fund your Lifetime ISA in the same tax year you open it – otherwise we’ll need to close it. So if you intend to fund your LISA by transferring in, it’ll need to complete before then end of the tax year.