The idea with a Gas Turbine is to allow a mid-high tier power generation option. It would be distinct from a Steam setup in that while it does need a warmup time, it is much faster to start up than a steam boiler. However it would still be relevant to a steam system as it would provide waste heat which could be used in a special boiler setup for it. This allows for high-efficiency combined cycle power production, at the major cost of a very limited fuel selection (Only refined liquid fuels and a certain few solid fuels, such as Coal Dust) and the high material cost for it.

@Generalcamo Will this replace the existing steam turbine?

Read the issue: it is designed to supplement it, not replace it.