It will probably depend on two things:
1) whether your variety is self-fertile or not, because some loquats require another variety to pollinate them

2) whether you have other insects that might do the job. I have adequate pollination in my garden without honeybees, because I have lots of bumblebees and various types of fly.

If you don't have pollinating insects at all, you may want to try brushing pollen around the flowers with a paintbrush.

I don't have first hand experience with this technique to say how successful it is, but if paintbrush pollination blossum by blossom is not a method you would consider, then you might try giving the tree a good shake every few days to simulate wind pollination.

Any hummingbirds? Those go for them in Seattle. There is a California species that has extended its range northward, is present during winter when the loquat trees bloom.

If there is ever a time when the greenhouse is being opened up for ventilation at the same time the tree is in bloom - and pollinators are present - these are likely to let themselves in.

There won't be any ventilation times any time soon. We are in consistent 38 day/18 night conditions.

There are fruit flies in the greenhouse but that's about it.

No hummingbirds in the greenhouse.

I had two big ones in the greenhouse that I pollinated by hand and I got a big crop. Use a paint brush and move from one flower to the next.

Bass