Perhaps you could push the partition column down into the referencing table
and add a constraint to keep them in sync. Example follows. I haven't tested
this with partitioning though.

CREATE TABLE Foo
(FooKey INT NOT NULL PRIMARY KEY,
 z INT NOT NULL /* partitioning column */,
 UNIQUE (FooKey, z));

CREATE TABLE Bar
(BarKey INT NOT NULL PRIMARY KEY,
 FooKey INT NOT NULL,
 z INT NOT NULL,
 FOREIGN KEY (FooKey, z) REFERENCES Foo (FooKey, z)
/* , other columns ... */);