create type sms_t as (
phid bigint,
message varchar(60),
received timestamp,
reason smallint)
instantiable
ref using bigint
mode db2sql;

create type winner_t under sms_t as (
prize_code char(6),
prize_id int,
mlid smallint,
sent timestamp,
msgid varchar(25))
mode db2sql;

create table sms_in of sms_t (
ref is smsid user generated,
phid with options not null,
received with options not null default current timestamp);

Created successfully.

create table winner of winner_t under sms_in inherit select privileges (
prize_code with options not null references prize_code,
prize_id with options not null references prize,
mlid with options not null references model);

Got SQL0901N The SQL statement failed because of a non-severe system error.
Subsequent SQL statements can be processed. (Reason "Error getting ftb for
the table".) SQLSTATE=58004

checked it - An error has occurred which is due to a system error. Processing
of the SQL statement has ended for reason "<reason>" (this is in
English only and is useful only to IBM support personnel).
Ok, so it is for IBM tech support only.

Changed the table a little bit:
create table winner of winner_t under sms_in inherit select privileges (
prize_code with options not null references prize_code,
prize_id with options not null,
mlid with options not null );

alter table winner add constraint fk2 foreign key ( prize_id ) references prize
alter table winner add constraint fk3 foreign key ( mlid ) references model

Created successfully.
The workaround exist, but still something is wrong with "references" in create typed table statement. The first "references" accepted, all next give the same error.

Published just in case some one is interesting in, or for IBM internal staff.