Yes and no. People in HK actually use slightly different 繁体字 then the people in Taiwan, so there is a version of Big5 called “Big5-HKSCS” (Hong Kong Special Character Supplement). For example, if you were to take the mandarin “是不是他們的?”, in Cantonese (HK) it would be written as “係唔係佢哋嘅?”. For more examples of interesting characters used in Hong Kong but not in Taiwan, see: Written Cantonese.
This translation site also has a few cantonese/mandarin translation examples that are worth taking a look at.
It’s OK for the HK people to read Taiwan-style Chinese text or for the Taiwan people to read HK-style text – they can understand the content without any problem, but that won’t make them as comfortable as reading the text in their own language style.
The tone of wording is also slightly different. When we say ZHHK, we must make the text read suitable for Cantonese speakers. When we provide ZHTW documents, we need to adapt it to mandarin tongues.
Therefore, for those text with great significance and extreme cultural sensitivity, for example the ads and important marketing brochures, we need to at least get them read through by the “native speakers” residing in either HK or Taiwan, thus to ensure your text delivers the right subtle feeling to the targeted audience.