If the taxpayer is an employee of a non-American employer, the individual will not be liable for FICA regardless of whether there is a totalization agreement unless a §3121(l) agreement is in effect.

Since P-Fund is considered a foreign pension/trust for US tax purposes rather than social security taxes (although it will most likely be treated as such for purposes of the totalization agreement once it is concluded), your client still has a whole host of issues to deal with.