Deacons (of any 'type', since there is only one Order of the Diaconate) are entitled, as clerics, to wear the Roman collar.
'Permanent' Deacons are excempt from the requirement to do so, and most choose not to.
Canon 284 gives the authority to regulate clerical attire to the local Bishops conference. Here is what the USCCB said
On November 18, 1998, the Latin Rite de iure members of the National Conference of Catholic Bishops approved complementary legislation for canon 284 of the Code of Canon Law for the Latin Rite dioceses of the United States.
The action was granted recognitio by the Congregation for Bishops in accord with article 82 of the Apostolic Constitution Pastor Bonus and issued by decree of the Congregation for Bishops signed by His Eminence Lucas Cardinal Moreira Neves, Prefect, and His Excellency Most Reverend Franciscus Monterisi, Secretary, and dated September 29, 1999.
Complementary Norm: The National Conference of Catholic Bishops, in accord with the prescriptions of canon 284, hereby decrees that without prejudice to the provisions of canon 288, clerics are to dress in conformity with their sacred calling.
In liturgical rites, clerics shall wear the vesture prescribed in the proper liturgical books. Outside liturgical functions, a black suit and Roman collar are the usual attire for priests. The use of the cassock is at the discretion of the cleric.
In the case of religious clerics, the determinations of their proper institutes or societies are to be observed with regard to wearing the religious habit.
As President of the National Conference of Catholic Bishops, I hereby decree that the effective date of this decree for all the Latin Rite dioceses in the United States will be December 1, 1999.
Given at the offices of the National Conference of Catholic Bishops in Washington, DC, on November 1, 1999.
Most Reverend Joseph A. Fiorenza
Bishop of Galveston-Houston
Reverend Monsignor Dennis M. Schnurr