It depends on the type of oxygen setup you are using and the mask or T-piece. With the standard trach mask or T-piece and a single source aerosol flow, the venturi may say 100% but it is doubtful if you will get much over 70% depending on the patient's tidal volume and overall minute volume or inspiratory flow demand. If you can run a double source flow or can score a high flow single system to that trach collar, you can get between 90 - 100%. A double source system is not impossible in an extended care facility if you have piped in oxygen. However, keeping someone in that facility who requires an FiO2 of 1.0 for any length of time would not be practical but that depends on the patient.
Now if you are just using a dry liter flow into a port adapter attached to the mask, you might be able to give as much as needed but only as high as that single flow meter will go and it would not be considered a "high flow" system. Also, if you are using a standard humified like you would use for a nasal cannula, you may be restricted to 6 Liters. A dry liter flow will eventually create mucus problems but could be used for the short term (< 1 - 2 hours depending on patient's hydration and secretions) or in an emergency.