Solar on clay tile roof and no underlayment

Background: moved into a SFH in April. The house and the roof is 50 years old. The roof is made of clay tiles and no underlayment. I think the roof has another 50 years of life.

Now when I get quotes for Solar, I get a separate quote for underlayment installation (around 20k). The solar quotes are around 40-44k (for a 8kw installation). Some companies are saying that it’s impossible to install on a clay tile roof. I’m getting mixed answers on how to get the roof ready for solar.

1. Is it true that solar cannot be installed on clay tile roofs? Should I get a new shingle roof just for Solar?
2. Will the underlayment installation be part of the rebate? The underlayment is purely to install solar.

Any help will be much appreciated!