Can the delivery time calculated by the plugin be used in Shopware product exports (data feeds)?

Yes, this is possible with the following code:

{% if product.extensions.acrisDeliveryTimeDelivery.value.available is defined and product.extensions.acrisDeliveryTimeDelivery.value.available and product.extensions.acrisDeliveryTimeDelivery.value.available.minDeliveryDays is defined and product.extensions.acrisDeliveryTimeDelivery.value.available.minDeliveryDays is not empty %}
    {% set calculatedDaysMin = product.extensions.acrisDeliveryTimeDelivery.value.available.minDeliveryDays %}
    {% set calculatedDaysMax = product.extensions.acrisDeliveryTimeDelivery.value.available.maxDeliveryDays %}
    {{ calculatedDaysMin }}
    {{ calculatedDaysMax }}
{% elseif product.extensions.acrisDeliveryTimeDelivery.value.notAvailable is defined and product.extensions.acrisDeliveryTimeDelivery.value.notAvailable and product.extensions.acrisDeliveryTimeDelivery.value.notAvailable.minDeliveryDays is defined and product.extensions.acrisDeliveryTimeDelivery.value.notAvailable.minDeliveryDays is not empty %}
    {% set calculatedDaysMin = product.extensions.acrisDeliveryTimeDelivery.value.notAvailable.minDeliveryDays %}
    {% set calculatedDaysMax = product.extensions.acrisDeliveryTimeDelivery.value.notAvailable.maxDeliveryDays %}
    {{ calculatedDaysMin }}
    {{ calculatedDaysMax }}
{% endif %}