With regard to being able to open your accommodation facility, you can do so under any of the alert levels. However, under levels 4 & 3 your guests will have to be under self isolation guidelines which may under alert level 3 require a minimum night stay period. This will require clarification.
In relation to recommissioning your property for reopening, our sector has seen police question staff travelling for the purposes of maintenance and general cleaning where Hotels have been closed. We have however in our own business authorised employees to carry out safety and security checks. Where our Hotels are operating and remember Hotels are deemed essential services, our staff have encountered no travel restrictions.
In summary, if your genuine intention is to open for guests you are permitted to go about your business. If it is to prepare for the future then this may be a grey area.
Hope this helps, TIA website may be a good source of further info.