The tailplane normally carries a download, holding the tail down and the nose up. Accretion of ice will raise the stalling speed of the tail. This should not be apparent unless large tailplane deflections are applied, in which case the tailplane is likely to be ineffective and allow the nose to fall. The best recovery action would be to allow the speed to rise and avoid sudden or gross back stick inputs. If ice is suspected it is generally good practice to keep the speed a bit higher than normal and avoid coarse manoeuvres.
Tailplane stall can be demonstrated on some aircraft by inducing a nose down pitch rate and then snatching the stick back. If the nose carries on down you've got it. On most types, however, the manufacturer will have limited the travel so that it is not possible to get into this predicament - at least with an ice-free tailplane.