I would refer back to NFPA 13R Standard for installation of sprinklers systems in residential occupancies up to and including four stories in height 2010 edition
Chapter 5 System components – section 5.2 Above ground Piping And Equipment that refers to the table 5.2.1 or accordance to 5.2.2
Table 5.2.1 speaks to the pipe being made of a metal. Where 184.108.40.206 When nonmetallic pipe is used, the pipe shall be designed to withstand a working pressure of not less than 175 psi (12.1 bar) at 120F (49C)
and 5.2.2 Types of pipe other than those specified in Table 5.2.1 shall be permitted to be used where listed for sprinkler system use.
And read on in section 5.2.2
I short if the owner could prove that the pipe meets the NFPA criteria then yes